Born in Greenock, Dorothea Maclagan studied at The Byam Shaw and Cole School of Art between 1914 and 1917. She then studied for five years at the Royal Academy Schools (1917-1922) where her tutors included Sir George Clausen and Ernest Jackson. Whilst at the Academy Schools, she won the Silver Medal for Drawing, the Armitage Prize, the Landseer Prize and the Landseer Scholarship.

She kept a studio in London throughout the 1920s and exhibited regularly at the RA, RPS and NEAC as well as in the Provinces and in Sweden and Holland. In 1929 she married fellow artist, Philip Douglas Maclagan (1901-1972). Meanwhile she had travelled extensively in Italy, France and Holland. Amongst her close artist friends were Glyn Philpot, Vivian Forbes and John Nash.

During the 1930s she moved to Meadle in the Vale of Aylesbury where she made a garden and began to specialise more in botanical work. After the War she had one woman shows in Cambridge (1947) and at Dartington Great Hall (1975). She continued to exhibit regularly in London and exhibited more than forty paintings at the Royal Academy during her career.

Her highly sensitive work, often on a small scale, reflects the influence of her thorough classical training. She delighted in ‘concentrated work' and botanical painting suited her meticulous watercolour style and precise observation. Her figure studies, whilst possessing great academic skill, also reveal a subtle and humane tenderness.