Tamm-Horsfall glycoprotein is the most abundant protein in human urine. The present investigation was planned to study the effect of Tamm-Horsfall protein (THP) on elaboration of virulence factors by biofilm cells of Pseudomonas aeruginosa. It was observed that with increase in concentration of THP from 10 to 50 μg/ml there was significant enhancement in elaboration of all the virulence factors by biofilm cells of P. aeruginosa. However, with further increase in concentration of THP from 50 to 70 μg/ml, significant decrease in elaboration of all the virulence traits was observed. Implications of these findings in relation to urinary tract infections caused by P. aeruginosa have been discussed.