The aim of this study was to evaluate the effect of Timolol maleate on tear film break-up time in a Nigerian population. 192 eyes of 96 subjects were examined in a hospital based case-control study after being administered pre-coded questionnaires. The mean tear film break-up time was measured. There was significant difference (t = 10.164, P < 0.001) in the mean break-up time of cases (10.45 secs) and controls (30.18 secs). Half of the cases had some ocular discomfort with the instillation of Timolol maleate, a significant number of them having just been commenced on the medication (chi2 = 8.889, P = 0.003). Long-term instillation of Timolol maleate impairs tear film stability. The ocular discomfort experienced by patients on Timolol may contribute to poor drug compliance observed in patients on chronic drug therapy. Regular screening of patients on Timolol maleate for tear film instability and dry eyes is important and drug manufacturers should explore the possibility of incorporating artificial tears in Timolol maleate preparation.