Background: Suicide rates among Alaska Natives in rural Alaska are almost 16 times higher than the national average. Some studies in northern latitudes have shown seasonal variation among suicide rates, with differences in patterns by age and sex, reasons for this variation and contributing factors are unclear. We modeled our hypotheses based on the assumption that vitamin D deficiency influences seasonal variation of suicide. We assessed the relationship between age, sex and seasonal variation of suicidal behavior in a rural region of Alaska. Methods: We utilized data from 804 individuals who exhibited lethal and nonlethal suicidal behavior (1990-2009). Information on age, sex, and potential contributing factors were recorded via a case report. We used multivariable logistic regression to identify the association between age, sex, and seasonality of suicide. Results: Among women, we observed a significant 41% increase in odds during season two compared to season one (OR=1.41, CI=1.06, 1.90); women had a significant 48% increase in odds during season two using data collected between 2002-2009 (OR=1.48, CI=1.04, 2.11). We did not observe any significant findings of seasonality with respects to age. The observed seasonal variation of suicide did not support vitamin D deficiency as an underlying cause, as increased incidence of suicide continued into the summer months when vitamin D deficiency would be less prevalent. Conclusion: We observed evidence of seasonal variation of suicidal acts by sex. Future studies of physiologic mechanisms influencing seasonality of suicide are important to target those at highest risk throughout the year.