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Key contacts
Managing Partner: Nele D’Halleweyn
Quick facts
Established

1920

Languages

Dutch, English, German, French

Key practice areas
Intellectual property
Trade mark
Patent
Patent prosecution
Trade mark prosecution
Trade mark prosecution - patent & trade mark attorney firms
Firm overview

Arnold & Siedsma is a full-service IP firm founded in 1920, offering a comprehensive range of services to protect and manage intellectual property. Our team of over 60 specialists, including patent attorneys, trademark and design attorneys, and legal experts, assist with the establishment of IP rights, advise on leveraging of IP, and represent clients in legal proceedings to enforce these rights.

With deep technical expertise across all major innovative sectors, our patent attorneys are equipped to handle even the most complex cases. In addition to patent services, we provide tailored IP strategy and management solutions, ensuring your innovations are safeguarded at every stage.

Arnold & Siedsma is a dedicated and experienced partner, committed to supporting you and your innovations every step of the way.

Last updated 21st November 2024

Practice Areas & Sector Specialisations

Key Practice Areas: Designs, Patent prosecution, Patent strategy & counseling, Trade mark prosecution, Trade mark strategy & counseling, Patent litigation, Trade mark litigation, IP transactions, Patent office proceedings, Trade mark office proceedings

Key Sector Expertise: Automotive, Biotechnology, Chemistry, Construction & materials, Computer technology & services, Electronics, Food & beverage, Healthcare, ICT & software, Life sciences, Medical device, Universities & research, Telecommunication, Semiconductors, Robotics, Renewable energy, Optics & photonics, Pharmaceutical, Nanotechnology, Artificial intelligence, Mechanical

Address:
Brand Whitlocklaan 114
Brussels
B-1200
Tel:+32 2 737 62 90 Email:Contact Us Web Address:http://www.arnold-siedsma.com

IPS Sponsored

  • Sponsored by Rouse
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2026 Edition
Patent prosecution
Tier 1
10 firms ranked
View full list

Tier 1

Arnold & Siedsma
6 practice areas
View full profile
De Clercq & Partners
1 practice area
View profile
Gevers
6 practice areas
View full profile

Tier 2

AWA
5 practice areas
View full profile
Brantsandpatents
6 practice areas
View profile
VO
4 practice areas
View full profile

Tier 3

Calysta
5 practice areas
View profile

Other Notable Firms

NLO
2 practice areas
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Oryon
4 practice areas
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Winger
5 practice areas
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Trade mark prosecution - patent & trade mark attorney firms
Tier 3
10 firms ranked
View full list

Tier 1

AWA
5 practice areas
View full profile
Gevers
6 practice areas
View full profile

Tier 3

Arnold & Siedsma
6 practice areas
View full profile
Brantsandpatents
6 practice areas
View profile
Calysta
5 practice areas
View profile
Kirkpatrick
6 practice areas
View profile

Tier 2

De Clercq & Partners
1 practice area
View profile
Novagraaf
3 practice areas
View profile
Winger
5 practice areas
View profile

Other Notable Firms

Oryon
4 practice areas
View profile
Overview

Arnold & Siedsma is a well-regarded patent and trade mark attorney firm in the Benelux. The firm has a strong team of European patent attorneys, with expertise in fields such as chemistry, biotechnology, electronics, and engineering. The chemistry patent practice grew in July 2020 following the acquisition of Belgian patent firm LC Patents. The firm merged with the Rouse Group in September 2025. Follow MIP's coverage of this firm here.

Notable patent practitioners: Paul Hylarides, Gerwald Verdijck, Steve Duxbury, Nele D'Halleweyn, Bart Laenen, Rogier Brouwer, Petri van Someren, Erik Bartelds, Martin Luten, Bart Jacobs and Remy Van den Bosch.

Notable trade mark practitioners: Joop Elzas and Sandra Bauwens.

Chemistry specialist Steve Duxbury is the managing partner.

Testimonials

2026

"Clear communication, tailored to our company's requirements and requests and with good follow-up. Very pragmatic and available in case of urgent questions or advice. Great knowledge of our business which helps them support and develop our IP strategy."

"Flexible, responsive, knowledgable. Propose the right strategies keeping outcome in mind."

"Good knowledge of our domain, clear advise on patent strategy, multiple in-house specialities, responsive."

"What I appreciate most about Arnold & Siedsma’s IP litigation service is the combination of deep technical expertise and a genuinely client-focused approach. The team demonstrates a strong ability to translate complex intellectual property issues into clear, practical strategies, which makes a real difference during high-pressure litigation. Their responsiveness and willingness to collaborate create a sense of partnership rather than just external counsel support."

"Overall, the service feels reliable, professional, and committed to achieving the best possible outcomes."

"What I particularly value about Arnold & Siedsma’s IP filing, prosecution, and administration service is the team’s reliability and precision. They consistently handle complex portfolios with a high level of accuracy and organization, which gives a strong sense of confidence that deadlines, formalities, and strategic considerations are all under control."

"The team is also approachable and responsive, making communication smooth and efficient. Their collaborative mindset makes them feel like an extension of the in-house team rather than just a service provider."

"The team is also very approachable and collaborative. They communicate complex IP matters in a clear and structured way, making it easier to make informed decisions. Their responsiveness and willingness to engage in discussions create a strong sense of trust and partnership."

"Overall, the advisory service stands out as knowledgeable, pragmatic, and genuinely focused on supporting clients in achieving their objectives."

Marten Bosma

"Communication is smooth, and support is readily available whenever urgent questions arise or when quick verification is needed."

Sara Reekmans

"Strong knowledge of our area, timely work, good advice."

Nele D'Halleweyn

"Nele D’Halleweyn stands out for her strong combination of technical expertise and clear, structured communication. She has a talent for breaking down complex IP matters into practical, understandable advice, which makes it much easier to navigate decisions with confidence. Her attention to detail and thorough approach ensure that work is consistently accurate and well-prepared."

 

2025

"Pragmatic, sensible advice and prompt delivery. I can trust and value their opinions."

"What stands out about Arnold & Siedsma's IP service is their professionalism, expertise, and client-focused approach.

"Their team combines deep technical knowledge with a clear understanding of our business goals, enabling them to provide tailored and strategic advice.

"We particularly appreciate their responsiveness, attention to detail, and proactive communication, ensuring we’re always informed and confident in our IP decisions."

"Their ability to deliver high-quality work while maintaining a collaborative and approachable style makes working with them both efficient and enjoyable."

Linked Reviews
Patent

Case studies show the firm handled patent filing, prosecution, and oppositions at the EPO. It also litigated before the UPC in a precedent-setting case for a medical device client. Patent trainees Hadewijch De Clercq and Julie Paddeu joined the firm in 2024.

Trade mark

Case studies show the firm advised on several infringement cases and handled a trade mark opposition for a dietary supplements company. Trade mark partner Karin Becks moved to Labels-IP in 2024.

Sunny Su explains how her team overcame challenges with orchard evidence collection to secure a favourable plant variety decision from China’s top court
Tech leads at three IP service groups discuss why firms need to move away from off-the-shelf AI products and adopt custom solutions
Tilleke & Gibbins topped the leaderboard with four awards across the region, while Anand & Anand and Kim & Chang emerged as outstanding domestic firms
The merger marks Rouse’s second M&A deal within a month, and will provide access to Arnold & Siedsma’s UPC offering
Only a few international law firms have made a mark in Australia’s IP market, but Rouse entering the field could be a sign of changing times
The 105-year-old IP firm Wrays and related business Aperture Insight will join Rouse but operate independently
A $110 million US verdict against Apple and an appellate order staying a $39 million trademark infringement finding against Amazon were also among the top talking points
Clients are divided on what externally funded IP firms bring to the table, so those firms must prove why the benefits outweigh the downsides
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