Senior User Experience Designer

3 Hours ago • 3-5 Years • UI/UX Design

Job Summary

Job Description

Critical Mass London is seeking a Senior UX Designer to create seamless and impactful user experiences for high-profile clients' digital products. The role involves translating complexity into clarity, organizing content, building information architectures, mapping user flows, and delivering high-fidelity wireframes and functional specifications. You will lead initiatives from concept to launch, shaping major features and refining processes. Responsibilities include designing holistic systems, drawing insights from data, guiding junior designers, managing time effectively, articulating complex ideas, and leading mid-level projects. A deep understanding of user experience, research, user-centered design techniques, and information architecture is essential.
Must have:
  • 3-5 years of UX experience in an agency environment.
  • Effective communication skills (oral and written).
  • Proven interpersonal and client relation skills.
  • Creative thinking and problem-solving abilities.
  • Detail-oriented, organized, and able to multitask.
  • Flexibility and adaptability to fast-paced environments.
  • Deep understanding of UX principles (research, user-centered design, IA, usability testing).
  • High proficiency in Figma, Keynote, PowerPoint, and Adobe Creative Suite.
  • Portfolio showcasing creative thinking, problem solving, and process.

Job Details

Critical Mass London is on the lookout for a talented Senior UX Designer to join our dynamic team and work with a high-profile, fast-paced client on cutting-edge digital experiences.

As a Senior UX Designer, you’ll be the driving force behind creating seamless and impactful user experiences for our clients’ digital products. With a sharp sense of self-awareness and a deep understanding of both user needs and business goals, you’ll translate complexity into clarity—crafting smart, intuitive journeys that deliver real value.

From organising content and building thoughtful information architectures to mapping user flows and delivering high-fidelity wireframes and functional specs—you’ll own it all. You’ll lead key initiatives from concept to launch, shaping major features and refining processes to ensure quality, consistency, and timely delivery at every stage.

You will:

  • Design holistic systems, flows, and interfaces that are simple, elegant, and beautiful through detailed wireframes, visual compositions, and prototypes that communicate design intent and client and user feedback.
  • Draw insights from data provided by web analytics and research studies, and turn those insights into tangible design solutions.
  • Provide guidance to members of the design team, constantly pushing the quality of our work..
  • Manage time effectively and execute according to commitments.
  • Apply a critical lens to your own work and the work of others.
  • Demonstrate team orientation, build rapport with creative teammates, and other internal teams.
  • Clearly articulate complex ideas to both the internal team and client.
  • Lead mid-level project work from a design perspective with autonomy and authority, facilitating design studios and working sessions to help the teams deliver the best possible solutions.
  • Continuously seek to be well-informed regarding new software and design concepts.Understand the process of business development and provide support by conducting relevant research, identifying key insights, and producing pitch materials with guidance from leadership.
  • Contribute to team culture by demonstrating a positive attitude, team-oriented approach, leadership qualities, and openness to learning and feedback.

You have:

  • 3-5 years of related industry experience in UX in an agency environment.
  • Effective communication skills, both orally and in a variety of written and diagrammatic forms.
  • Proven interpersonal skills, client relation skills, and ability to work in a team environment.
  • Proven track record of creative thinking and solving challenges with intuitive and engaging design solutions.
  • A thorough, detail-oriented, and highly organised working style with the ability to multi-task and meet tight deadlines.
  • Flexibility and adaptability to fast-paced and changing environments.
  • A deep appreciation and understanding of user experience, including research, user-centered design techniques, information architecture, usability testing—and applying it to create compelling digital experiences for large scale platforms.
  • High proficiency in the use of Figma as well as Keynote, Powerpoint, and Adobe Creative Suite.
  • Portfolio of work demonstrating creative thinking, problem solving, process, and quality spanning various digital platforms.

Our new hires & employees are the future of our organization, and we want to set you up for long-term success.  In an effort to do so, we expect our team to work from an office a minimum of 3 days a week.

Critical Mass is an equal opportunity employer. 

The Critical Mass Talent Acquisition team will only communicate from email addresses that use the URLs criticalmass.com and us.greenhouse-mail.io. We will not use apps such as Facebook Messenger, WhatsApp, or Google Hangouts for communicating with you. We will never ask you to send us money, technology, or anything else to work for our company. If you believe you are the victim of a scam, please review your local government consumer protections guidance and reach out to them directly.

If U.S. based: https://www.consumer.ftc.gov/articles/job-scams#avoid
If Canada based: https://www.canada.ca/en/services/finance/consumer-affairs.html
If U.K. based: https://www.gov.uk/consumer-protection-rights
If Costa Rica based: https://www.consumo.go.cr/educacion_consumidor/consejos_practicos.aspx 

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About The Company

Critical Mass is a team of 1,800 inspired folks based in 12 offices around the world, providing full-service digital capabilities for the greatest brands on Earth. Our secret sauce is our uncompromising design standards, our relentless focus on customers, and an ability to put powerful new technologies to work for our clients.


We work with the best—Apple, Nike, Mars Wrigley, Nissan, Diageo, Airbnb, BMW, BNY Mellon, Johnson & Johnson, and many more—brands who strive for connected digital ecosystems and unparalleled experiences. We help them get there by gaining deep insight into their consumers and orchestrating data, AI, design, media, and tech stacks around human stories.


We’re a global agency founded in Canada, but digital is our home. If you know us, then you know we’re a special, quirky place that attracts big talent and tiny egos. (We actually give out a “so f-n nice” award—lots of them). But just because we’re friendly doesn’t mean we’re not a force to be reckoned with. We’re driven. Relentless. And we live our values. We’re Critical Mass, but our friends call us CM. Please call us CM!

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