The study was carried out to determine the effects of levels of crude fibre (CF), with and without a probiotic (PB) - Saccharomyces cerevisiae – on the growth, haematology, and serum biochemistry of weaner pigs. Forty-eight (48) 11 week (wk) old F1 Large White (LW) x Landrace (LR) (LW x LR) crossbred weaner pigs of mean weight 10 kg were used for the study which lasted for 11 wk. The study was a 2 x 4 factorial involving 8 treatments (T₁-T₈) and 3 replications/treatment (6 piglets/treatment, and 2 piglets/replicate) namely: T₁: 5% CF + 0.00g PB; T₂: 10% CF + 0.00g PB; T₃: 5% CF + 0.50g PB; T₄: 10% CF + 0.50g PB; T₅: 5% CF + 0.75g PB; T₆: 10% CF + 0.75g PB; T₇: 5% CF + 1.00g PB, and T₈: 10% CF + 1.00gPB/kg. Two isocaloric and isonitrogenous diets having two CF levels (5 or 10%) were formulated for the experiment. The probiotic was added to the feeds after compounding. Results showed significant (P<0.05) effect of treatment on growth, linear body parameters, and serum biochemical indices of the pigs but not on the haematological indices. It was concluded that the combination of 5 or 10% CF with 0.75gPB/kg diet was found the best to enhance the growth of crossbred weaner pigs. However, some of the blood and serum biochemistry values of the pigs were suboptimal.