Larkin (pictured) was previously chief executive at software and servicing company Target.
He has previously held senior roles at Lloyds and Virgin Money.
Earlier this year, Trussle co-founder Ishaan Malhi quit the company as boss.
The digital adviser was founded in 2015 by Malhi and Jonathan Galore.
New investor Rabo Frontier recently injected another £7.5m into the business, following existing investors Goldman Sachs and Finch Capital.
Larkin said: “The home ownership journey is one of the most stressful experiences that consumers face, yet not enough has been done to simplify the process for both homeowners and lenders.
“There’s a tremendous opportunity to leverage technology to transform home financing and mortgage distribution, making the market work better for homeowners and lenders.
“The Trussle team has done a great job so far, and our excellent group of investors are committed to the strategic opportunity that lies ahead. Trussle is really well positioned to lead the transformation of the mortgage industry.”
Simon Williams, Trussle’s chairman, added: “We are thrilled to have someone of Ian’s calibre leading the business. Ian’s vast experience in retail and commercial financial services, and his expertise in growing businesses and enhancing customer propositions will be an important part of our success.
“We are at a pivotal stage of Trussle’s journey and look forward to working closely with Ian to build on our vision of making home ownership more accessible to everyone.”