Background <p>There is growing interest in understanding if, and how, the menstrual cycle may affect physical and cognitive performance, particularly in the context of sport and physical activity. While hormonal fluctuations are often assumed to impact cognition, especially during menstruation, empirical evidence remains inconclusive. This study aimed to investigate whether cognitive performance, mood, and symptomology vary across menstrual cycle phases and whether these effects are influenced by athletic participation level.</p> Results <p>Fifty-four females (18–40 years) categorised by athletic participation level (i.e., inactive, active, competing, elite) took part. At each key menstrual phase (menstruation / early follicular, late follicular, ovulation and mid-luteal), they completed a cognitive battery (attention, inhibition and spatial anticipation), and reported their mood and symptoms. Faster reaction times and fewer errors were committed during ovulation (<i>p</i> &lt; .01), suggesting better overall performance. In contrast, reaction times were slower during the luteal phase (<i>p</i> &lt; .01), but more errors were committed in the follicular phase (<i>p</i> = .01). Importantly, participants’ athletic level had a stronger effect on cognitive performance than phase, where inactive participants scored worse across tasks than their more active counterparts, and elite participants exhibited more significant fluctuations in cognition across phases. Mood and symptoms were worse during menstruation regardless of athletic level. However, while mood varied across phases it did not correlate with cognitive performance. Of note, participants perceived that their symptoms negatively impacted their cognitive performance during menstruation, but there was no evidence of any objective detriment to cognitive performance during this phase neither on reaction times nor errors on any task.</p> Conclusion <p>These findings suggest the existence of mild cognitive fluctuations throughout the menstrual cycle, albeit with high individual variability, and which are incongruent with symptomology. Opposing results between perceived and measured performance challenge common assumptions about menstruation-related performance, and highlight the importance of addressing societal biases in female sport and health. The stronger effects of athletic engagement on cognitive performance, rather than phase, reinforce the cognitive benefits of an active lifestyle.</p> Key Points <p>This study aimed to investigate cognitive fluctuations in eumenorrheic females recruited from a range of activity levels.</p> <p>We demonstrate mild cognitive fluctuations throughout the menstrual cycle, which are incongruent with symptomology.</p> <p>And reinforce the importance of physical activity for supporting cognitive performance.</p>