Simonida was discovered on 20 March 1938, by Serbian astronomer Milorad Protić at Belgrade Astronomical Observatory. On the same night, it was independently discovered by Belgian astronomer Fernand Rigaux at Uccle Observatory in Belgium.
The S-type asteroid asteroid is a member of the Flora family, a large population of stony asteroids in the main-belt. It orbits the Sun at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,219 days). Its orbit has an eccentricity of 0.12 and an inclination of 7° with respect to the ecliptic. Simonida's first observation was a precovery taken at Lowell Observatory in 1931, extending the body's observation arc by 7 years prior to its official discovery observation.
In March 1988, Polish astronomer Wiesław Z. Wiśniewski obtained a lightcurve of Simonida that gave a rotation period of 5.3 hours with a brightness variation of 0.26 magnitude (U=2). In January 2004, astronomer A. Kryszczynska at Poznań Observatory measured a period of 5.2885 hours with an amplitude of 0.50 magnitude (U=2+). In January 2008, photometric observations by astronomers Martine Castets, Bernard Trégon, Arnaud Leroy and Raoul Behrend gave a rotation period of 5.16 hours with a brightness variation of 0.21 (U=3-).
According to the space-based Japanese Akari satellite, Simonida measures 12.16 kilometers in diameter, and its surface has an albedo of 0.211. The Collaborative Asteroid Lightcurve Link, however, agrees with the results obtained by 8 observations of the Infrared Astronomical Satellite IRAS, that gave a diameter of 11.08 kilometers and an albedo of 0.25 with an absolute magnitude of 11.9.
This minor planet was named for Byzantine princess and queen consort Simonida, the wife of medieval Serbian king Stefan Milutin and symbol of beauty in former Yugoslavia. The official naming citation was published by the Minor Planet Center before November 1977 (M.P.C. 3359).