Delayed emission from a-terthiophene (3T) and a-quinquethiophene (5T) in a perhydrotriphenylene (PHTP) host is investigated. Delayed fluorescence for the lowest singlet excited state of 3T and 5T is detected at both low (80 K) and room temperatures. In addition, at low temperature, phosphorescence from 3T is observed with a lifetime of 100 µs. Comparison of the dependence of delayed fluorescence and phosphorescence on excitation intensity and time shows that delayed fluorescence does not originate from triplet–triplet annihilation. A dependence of the delayed fluorescence on atmospheric pressure indicates that it originates, at least partially, from complexes of photoexcited oligothiophene and molecular oxygen O2.