Informal learning is becoming a standard format in companies' training and development (T&D) activities. It requires a specific learning competence comprising cognitive, metacognitive, and motivational dimensions. In the present study, it was investigated whether learning-competence variables predict success in informal learning. Given the ageing of the workforce, we also explored age differences in learning competence in an online survey of 470 workers in three age groups (17-35, 36-50, and 51-65 years old) at a German mail-order company. Learning competence predicted success in informal learning independent of worker age, but was partially mediated by memory self-efficacy, which might induce "second-order" age effects under unfavourable T&D conditions. (Contains 10 tables.)