Adolescents' secrecy is intertwined with perception of parents' behaviors as acts of privacy invasion. It is currently untested, however, how this transactional process operates at the within-person level-where these causal processes take place. Dutch adolescents (n = 244, Mage = 13.84, 38.50% boys) reported three times on perceived parental privacy invasion and secrecy. Cross-lagged panel models (CLPM) confirmed earlier findings. Privacy invasion predicted increased secrecy, but a reverse effect was found from increased secrecy to increased privacy invasion. Controlling for confounding positive group-level associations with a novel random intercept CLPM, negative within-person associations were found. Higher levels of secrecy predicted lower levels of privacy invasive behaviors at the within-person level. These opposing findings within- versus between-persons illustrate a Simpson's paradox.