Premenstrual dysphoric disorder is a somatopsychic condition that develops about a week before the start of menstruation and is brought on by fluctuating sex steroid levels that follow an ovulatory menstrual cycle. Therefore, this study aimed to assess the magnitude of premenstrual dysphoric disorder and associated factors among Haramaya University graduating class female students, in eastern Ethiopia. An institutional-based cross-sectional study was conducted from 1 to 30 November 2022 among Haramaya University graduating class female students using a simple random sampling technique. The data were cleaned, coded, and entered into the Epi-data 3.01 before being exported and analyzed with Statistical Package of Social Science 20 versions. The premenstrual dysphoric disorder was assessed by the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision. To identify associated factors a bivariable logistic regression analysis was conducted to determine the association between each independent variable and the outcome variable. The multivariable logistic regression model includes all variables with a -value of less than 0.25 in the bivariate logistic regression analysis. The adjusted odds ratio with a 95% confidence interval was computed when the -value was less than 0.05, which was considered statistically significant. Out of 282 samples, 274 study participants were involved providing a response rate of 97.2%. The prevalence of premenstrual dysphoric disorders was 64.6% (95% CI: 59.5-70.4). Participants with the irregular menstrual cycle (AOR = 2.24; 95% CI: 1.26-4.34), heavy menstrual flow (AOR = 2.53; 95% CI: 1.84-7.59), moderate menstrual flow (AOR = 2.29; 95% CI: 1.02-5.26), severe menstrual pain (AOR = 5.69; 95% CI: 1.86-7.42) and those who have depressive symptoms (AOR = 2.46, 95% CI: 1.08-5.68) were variables associated with premenstrual dysphoric disorders. The prevalence of premenstrual dysphoric disorder was relatively high. Severe menstrual pain, menstrual irregularity, heavy menstrual flow, and a history of depression had significant associations with premenstrual dysphoric disorder. It will be better if higher institution administrators design and implement methods to screen and intervene premenstrual dysphoric disorder among female students.