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This study aimed to investigate the antibacterial [minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)] and antibiofilm activity [log10 colony forming unit/mL (CFU/mL) and biofilm disruption] of copper-doped phosphate glass (CDPG) against <i>Streptococcus oralis, Enterococcus faecalis, Lactobacillus casei, Staphylococcus aureus, Escherichia coli,</i> and <i>Pseudomonas aeruginosa</i>. Methods: the antibacterial activity was determined using microbroth dilution and time-kill assay. The antibiofilm activity was investigated using crystal violet and confocal laser scanning microscopy. Bacteria growing in absence of CDPG were used as controls. Results: the MIC was ≥125 mg of CPDG/mL; the log10 CFU/mL reduction ranged from 2.66–3.14 to 6.23–9.65 after 4 and 24 h respectively. Generally, no growth was observed after 24 h of treatment with CDPG; the MBC was 250 mg/mL for <i>L. casei</i> and <i>S. oralis</i> while 500 mg/mL for the rest of the bacteria. The highest and lowest antibiofilm activity was observed against <i>S. oralis</i> and <i>E. coli</i> respectively. Three patterns of complete biofilm disruption were seen: (i) large areas with <i>E. fecalis</i> and <i>S. oralis</i>, (ii) medium-size pockets with <i>S. aureus</i> and <i>P. aeruginosa,</i> or (iii) small areas with <i>E. coli</i> and <i>L. casei</i>. Conclusion: CDPG can be potentially used as an antibacterial and an antibiofilm agent against oral biofilm-forming bacteria.