Weightmans and Ward Hadaway have abandoned plans to merge after four months of talks.
A tie-up would have created a northern-headquartered firm with a turnover of around £130m.
However, both firms said their strategies were not sufficiently aligned for a merger to work.
Weightmans managing partner John Schorah said: “We have many common interests, but after discussions it became clear that we each want different things from our respective futures.
“We sensibly agreed between us it was better to focus on those things.”
Ward Hadaway head Jamie Martin meanwhile added: “We wish to continue to pursue our strategy of developing a ‘Northern Law Firm for National Business’ across our three offices in Newcastle, Leeds and Manchester and our focus on providing legal services to Northern-based businesses.”
Weightmans would have been the larger of the two firms, with turnover reaching £95m in 2015/16.
Ward Hadaway’s revenue totaled £35.8m but its average profit per equity partner would have been over £100,000 larger than Weightmans at £352,000.
When merger discussions began in January, Schorah said: “The legal market is changing and it is always sensible to look at opportunities that might benefit a business, its clients and its staff.”
He added: “We have shared strategic objectives and a significant number of shared clients.”