The incidence of catheter-associated urinary tract infections in cats catheterised for an obstructive lower urinary tract disease (LUTD) has not previously been evaluated. The objective of this study was to evaluate the frequency of significant bacteriuria in cats with obstructive LUTD managed for 48 h with a closed urine collection system. Eighteen male cats admitted for a non-infectious obstructive LUTD were evaluated. This was a prospective study. A standard protocol was used for aseptic catheter placement and maintenance. Three urine samples were collected from each animal through the catheter immediately after placement, 24 h after placement and just before removal. All samples underwent complete urinalysis, including bacterial culture. Catheter tips were tested by bacterial culture. Six cats (33.3%) developed significant bacteriuria during catheterisation. The causative bacteria were common feline uropathogens (Escherichia coli, Staphylococcus species) in five cases, and Streptococcus bovis in one. One cat developed a fungal infection. The presence of bacteria in urinary sediment was correlated strongly with positive urine culture results. The catheter tips from 10/18 cats (55.5%) were positive for culture. The positive predictive value of a positive culture from the urinary catheter tip was 87.5%. The specificity was 53.8%. The same infectious agents were cultured from both urine and catheter tip in six cases. In summary, one-third of cats developed significant bacteriuria during catheterisation. Silent bacteriuria could not be clearly differentiated from true urinary tract infection. The presence of bacteria in the urinary sediment was strongly indicative of bacteriuria. The specificity of urinary catheter tip culture was low.