Imagining personal future events is associated with well-being, but the nature and direction of this relationship are unclear. This study investigated whether imagining episodic future scenarios, experimentally manipulated for valence, have an immediate impact on affect. University students (N = 197) completed a 2 × 3 between-subject online study in which they imagined four personal events likely to occur in the future. Participants were directed to imagine positive or negative events or were undirected as to valence to additionally assess the valence and effect of self-directed imagined scenarios. Participants in all three conditions reported a change in positive affect immediately after the task, with both positive and nondirected thinking improving positive affect and negative future thoughts reducing it. However, negative affect only shifted in response to negative future thinking but not the other conditions. These findings demonstrate that there is an immediate causal effect of episodic future thinking on affect but only in specific directions and that this differs from the patterns shown in longer term measurements. The findings also suggest when self-directed that imagined future thoughts tend to mirror the valence and causal effect of positively induced thoughts. This study has implications for the ongoing debate around future thinking and well-being.