The study investigated the association between lower urinary tract symptoms (LUTS) and sexual dysfunction in ageing men. It was a cross-sectional study in an unselected consecutive sample of 398 men aged >40 years attending a urology clinic. LUTS and sexual function were assessed by validated symptom scales, including the International Prostate Symptom Score (IPSS) and the International Index of Erectile Function-5 (IIEF-5). Clinically the severity of total and obstructive IPSS showed no significant correlation with age, but irritative IPSS is statistically correlated with age (P < 0.05). The prevalence of moderate to severe ED (IIEF-5 < 12) was significantly associated with LUTS severity (P < 0.05) and the severity of IIEF-5 correlated significantly with age (P < 0.01). A consistent inverse correlation was found between IIEF-5 and IPSS severity across the age groups, with the strongest effect within aged 60 to 69 years (r = −0.286, P < 0.01). The irritative IPSS showed a significant correlation with IIEF-5 severity across all age groups. These results reveal a significant correlation between LUTS and the severity of ED, especially on the irritative domain.