Dinosaurs have been a very popular science topic since signs of their presence on earth were first discovered. They have represented so-called "edutainment" for some people. Learning from informal sources and in- an out-of-school environment can be effective and motivating. In this study, 12-year-old pupils (N = 366) visited a dinosaur science centre exhibition in Finland. Pupils were tested with standardised tests of motivation as defined by self-determination theory, cognitive skills, and interest via pre-, post-, and delayed post-tests during a six-month period. Findings show that pupils learned from the science centre visit and enjoyed the experience. The factors explaining their post-test knowledge in addition to their previous knowledge were (1) general cognitive competence, (2) liking studying biology at the science centre, (3) participation in a dinosaur demonstration, and (4) gender. As there was no difference between boys and girls in general cognitive competences, the knowledge results of boys and girls equally related to their cognitive competence. Autonomy also influenced situational motivation both directly and indirectly, which in turn had a strong effect on liking studying in the exhibition. It also influenced the post-test knowledge indirectly. In the lowest school achievement group, participation in the dinosaur demonstration increased knowledge in the post-test.