Two experiments (N = 256 university students) tested whether personal task choice can attenuate previously found implicit affective influences on cardiac responses reflecting mental effort. Based on a recent action shielding model (Gendolla et al., 2001), participants could ostensibly either personally chose characteristics of an upcoming cognitive task or not. In Experiment 1, replicating previous research, priming anger resulted in stronger PEP responses than priming sadness in an assigned objectively difficult memory task. Most relevant, this replicated affect prime effect disappeared when the task could ostensibly be personally chosen. In Experiment 2, priming sadness resulted in stronger PEP responses than priming happiness. Also this affect prime effect disappeared when participants could ostensibly choose their task, resulting in strong PEP responses reflecting high effort in both affect prime conditions. This pattern suggests that participants tried to do their best in the memory task and provides the first evidence for choice induced shielding against the effects of positive affect on effort intensity. Taken together, the present experiments’ findings match with other recent evidence showing that personal action choice shields against incidental affective influences on action execution and especially on effort-related cardiovascular response (e.g., Bouzidi & Gendolla, 2023; Falk et al., 2022a, 2022b).