Background Grand multiparity has been associated with increased risks of adverse pregnancy outcomes such as post-partum hemorrhage,gestational hypertension, gestationaldiabetes mellitus and high perinatal mortality.There is limited information about the impact of high parity on pregnancy outcomes in Tanzania. This study aimed to determine prevalence, trend and associated adverse pregnancy outcomes of grand multiparity in a tertiary hospital in Northern Tanzania. Methods A retrospective cross-sectional study was conducted at Kilimanjaro Christian Medical Centre (KCMC) using maternally linked data from medical birth registry. Women with singleton deliveries from 2006 to 2014 were analyzed. The prevalence of grand-multiparity was computed as proportion to estimate the trend over years. Adverse pregnancy outcomes associated with grand multiparity were estimated using multivariable logistic regression models. A p -value of < 0.05 was considered statistically significant. Results The overall prevalence of grand multiparity was 9.44% ranging from 9.72% in 2006 to 8.49% in 2014. The grand multiparous women had increased odds of prelabour rupture of membranes (Adjusted odds ratio [AOR] 1.78: 95% CI:1.28–2.49), stillbirth (AOR 1.66: 95% CI:1.31–2.11) and preterm birth delivery (AOR 1.28; 95% CI: 1.05–1.56) as compared to women in the lower parity group. Conclusions The prevalence of grand multiparity among women in North-Tanzania was 9.44%. It was significantly associated with adverse pregnancy outcomes. This calls for a need to increase community awareness on its risks, encourage birth control among older women. Delivery-care facilities should prepare for emergency situation when attending deliveries of high parity group.