Background <p>Slow change blindness, when attentive observers fail to notice large changes that happen gradually, raises questions about how visual information is combined across time. One plausible integration strategy is serial dependence: blending information from the recent past into current perception. We investigate serial dependencies in perception of a cartoon object that slowly changes hue. In a one-shot experiment, observers each viewed a single trial with a random degree of hue change and provided one hue judgment response. Across participants, the entire morph was probed.</p> Results <p>Observers’ hue reports revealed an overall bias toward the past that increased in magnitude as more of the morph was experienced. In three follow-up experiments, we verified that observers experienced slow change blindness, confirmed that the bias was serial dependence, and replicated the results with a repeated-trials design.</p> Conclusions <p>Overall, we provide evidence that serial dependence actively biases perception during gradual changes, sometimes producing slow change blindness.</p>