Traditional medicine is widely used, but its effectiveness is often questioned. Biofilm-producing bacteria and fungi are important in difficult-to-treat persistent and recurrent infections. The present study investigated the anti-biofilm properties of crude methanolic extracts from three medicinal plants used in Namibia, namely Aptosimum albomarginatum (Marloth and Engl.), Albizia anthelmintica (A. Rich Brongn.) and Dicoma schinzii (O. Hoffm.). Biofilm formation, inhibition and eradication were determined using microtiter plate assay. Extracts were tested against Escherichia coli ATCC 700928, Staphylococcus aureus ATCC 12600, S. aureus U3300, Bacillus subtilis ATCC 13933, Streptococcus mutans ATCC 25175, Streptococcus sanguinis ATCC 10556, Pseudomonas aeruginosa and Candida albicans. All isolates were strong biofilm producers. A. albomarginatum root extract moderately inhibited biofilm formation in S. mutans ATCC 25175 (60.0%), E. coli ATCC 700928 (51.6%) and P. aeruginosa (49.1%). A. anthelmintica twigs caused 58.4% biofilm inhibition in C. albicans and eradicated S. aureus U3300 biofilm by 74.8%. D. schinzii leaf extract inhibited P. aeruginosa biofilm by 67.3%, and in addition broke down S. mutans ATCC 25175 biofilm by 44.2%. These results validate the usefulness of the three plants as traditional medicine in some instances. Keywords: Aptosimum albomarginatum, Albizia  anthelmintica, Dicoma schinzii, traditional medicine, antibiofilm activity, flavonoids, saponins.