Objective In cross‐sectional studies, positive affect (PA) has been associated with higher levels of cognitive functioning. This study examined whether positive affect (PA) is associated with change in cognitive function over 12 years in an adult population sample. Methods Participants (n = 258), aged 40 to 82 years, were drawn from a subsample of the Maastricht Aging Study (MAAS) and assessed at baseline, 6 years and 12 years. PA was measured at baseline with a Dutch translation of the Positive and Negative Affect Schedule (PANAS). PA scores and associations with cognitive decline were tested in random‐effects models. Results Controlling for demographics and depressive symptoms, there was no significant association with PA scores and decline in memory (χ2 = 1.52; df = 2; P = 0.47), executive functions (χ2 = 0.99; df = 2; P = 0.61), and information processing speed (χ2 = 0.52; df = 2; P = 0.77) at 6‐ and 12‐year follow‐up. Conclusions PA did not predict cognitive change over time. These findings question the extent of protective effects of PA on cognitive aging in adulthood, and are discussed in terms of age range and types of measures used for PA and cognition.