The architecture firm made the top ten of a survey of British workplaces, and was recognised for its training provision in a separate award.
Assael was placed 7th in the 'Sunday Times 100 Best Small Companies to Work For' survey and praised for its 'robust commitment to training and personal development'.
Other architects to make the list are Jestico + Whiles, BPTW Partnership and HLM Architects, who were placed 50, 63 and 85 respectively.
Practice chief John Assael ( pictured above right) said: 'We have always recognised the importance of looking after all our staff, regardless of their position in the company.
'This result means that we are definitely on the right track.
'We are all very pleased and I personally am very honoured with the outcome.'