The move will give Artemis a "significant minority shareholding" in the Edinburgh-based company, which has already received £1m from its founders.
Set up by former Ernst & Young partner Eamonn Rice, mform is due to launch in the autumn, entering an already competitive market that includes moneysupermarket.com, moneynet.co.uk, confused.com and SMG's PeoplesChampion.com.
Rice told The Scotsman that mform would have a number of unique features and aim to compete with traditional mortgage brokers, particularly for remortgages. He aims to break even within 12 months of launch and hit revenues of £10m within three years.
He said: "With well over 6,000 mortgages from more than 100 lenders to choose from, many consumers find the process of choosing a mortgage product to be complicated and stressful. It does not need to be and we aim to make it simple, fast and efficient.
"We are targeting a significant share of the residential mortgage market. We are delighted that Artemis is backing us because it has a great reputation for picking winners."