Inksters, the first firm in Scotland to have its own YouTube channel and Twitter feed, has used the money to purchase and refurbish premises in Glasgow.
The move from Wellington Street to the Exchange Building on St Vincent Street in the city has been backed by Bank of Scotland.
The new office is around three times the size of the former premises and the additional space will see Inksters expand from 11 people to 14 in the short-term with further hires pencilled in for 2014.
Experienced commercial and domestic property lawyer John McKissock is the first of the new recruits to formally join.
In recent years the firm has expanded outside of Glasgow and also has offices in Inverness, Wick and Portree. It operates in legal sectors including family, property, debt recovery as well as niche areas including crofting.
Founder Brian Inkster said: "Inksters has expanded from just myself and a secretary in 1999 to employing 11 staff in four locations throughout Scotland.
"Opening our new headquarters in Glasgow marks a major boost for the business, creating extra room for growth and a determination to continually improve the service we offer our clients.
"Immediately we will increase our headcount in Glasgow by three with further hires taking place throughout 2014."
Although the firm declined to give its turnover figures, Mr Inkster said it expects to grow by 50% next year.
Turnover was said to have increased by 22% and profits by 37% in the most recent financial year.
He said: "Specialising in niche areas of law has helped us secure a strong reputation that we're planning to continue to develop across Scotland in the future, capitalising on our forward thinking approach and technological investment."
Mr Inkster indicated he was keeping an open mind on the hiring of additional staff and whether that may take the firm into other practice areas.
He said: "This is fluid and may be dependent as much on the solicitors who want to work for Inksters, and we want to work with, than areas we may wish to strengthen or expand into."
Craig McSporran, relationship manager at Bank of Scotland, said: "Solicitors are at the heart of business communities and society throughout Scotland, advising small businesses and families in legal matters ranging from employment law to house purchases to executries.
"At Bank of Scotland we recognise the pivotal role played by the legal profession in building the economy, and we're keen to support them in their own growth.
"We've received specialist training from the Law Society of Scotland, including in their Practice Management Standard. We were the first bank in Scotland to provide this sort of training, and we know how important it is to keep our sector knowledge up-to-date."