Abstract Previous research has emphasized the beneficial role of biospheric and altruistic values in promoting pro‐environmental behavior, whereas egoistic values have been considered hindrances. We challenge the hindering role of egoistic values for pro‐environmental behavior by suggesting the counterintuitive idea that egoistic values positively predict environmental activism over time. Furthermore, drawing from self‐perception theory, we argue that environmental activism positively predicts egoistic values over time. We tested our hypotheses using data from 1369 employees in Germany who responded to two surveys three months apart. Consistent with expectations, results showed that egoistic values positively predicted (changes in) subsequent private and work‐related environmental activism, as well as involvement in environmental activism groups (but not self‐oriented pro‐environmental behaviors or mere support of environmental activism groups). Additionally, private and work‐related environmental activism positively predicted (changes in) subsequent egoistic values. Overall, these findings advance the literature on pro‐environmental behavior by demonstrating the beneficial role of egoistic values for environmental activism and by showing reciprocal relations between egoistic values and pro‐environmental activism across time in both private and work contexts.