Although the tradition of theatre in Koper goes back to the times of the Venetian Republic in the 15th century, professional theatre was only active in Koper for a few years in the 1950s. Then in 2000 Koper-Capodistria Urban Municipality established Koper Theatre, an ensemble which comprises mainly guest actors, presenting an annual repertory programme of around six premieres. Some productions have received awards at the Days of Comedy festival in Celje and at the Slovene Festival of Chamber Theatre (SKUP) in Ptuj. Koper Theatre also hosts several performances by Ljubljana City Theatre (MGL), Slovene National Theatre (SNG) Nova Gorica, Špas Theatre, Prešeren Theatre Kranj and other institutions.

Koper Theatre takes part in producing the Primorska Summer Festival, Koper-Capodistria and the Slovene Puppetry Biennial. Together with Obalne galerije - Coastal Galleries it publishes the GledGa newsletter on cultural events in the city. The company has recently begun co-operating with Avditorij Portorož (see Portorož Auditorium) and with the University of Primorska.