Brother of Philippos Margaritis, he studied painting and lithography in Paris. In 1836 he returned to Athens and was appointed the first Professor of Painting at the Evelpidon (Military Cadet) School. At the same time he founded a painting studio, in which he also installed lithography apparatus. His brother also established himself there after his return to Greece and there is mention made that the Prime Minister Ioannis Kolettis visited it in 1844. Moreover, they later founded the first photography studio in Athens, introducing the art of photography to Greece. From 1843 to 1853 he taught, without pay, Advanced Painting, Plaster Work and Oil Painting at the School of Arts.
Georgios Margaritis, influenced by the neoclassical spirit, did portraits of warriors and various personalities of the period with a tendency toward beautification and idealization, but also scenes from the Greek War of Independence, such as the work “Karaiskakis Advances on the Acropolis”, and “Karaiskakis Wounded at the Battle Along the Coast” the drawing for which earned him a silver medal in 1870 at the Olympia exhibition. Moreover, in cooperation with his brother, he decorated the palace with wall paintings, the Throne Room in particular.