The men's 400 metre freestyle competition of the swimming events at the 1971 Pan American Games took place on 8 August.

[1][2] The last Pan American Games champion was Greg Charlton of US.

[3][4][5][6][7][8] This race consisted of eight lengths of the pool, with all eight being in the freestyle stroke.

[9] All times are in minutes and seconds.

The final was held on August 8.