Investigations of antibacterial activities revealed that the incorporation of longer alkyl chains to the C-6 position in resorcylic acid conferred antibacterial properties against Staphylococcus aureus and Bacillus subtilis. The resultant olivetolic acid (OA) derivatives with n-undecyl and n-tridecyl side-chains, even those lacking the hydrophobic geranyl moiety from their C-3 positions, exhibited strong antibacterial activities against B. subtilis at a MIC value of 2.5 μM. Furthermore, the study demonstrated that the n-heptyl alkyl-chain modification at C-6 of cannabigerolic acid (CBGA) effectively enhanced the activity against B. subtilis, demonstrating the importance of the alkyl side-chain in modulating the bioactivity. Overall, the findings in this study provided insight into further evaluations of the antibacterial activities, as well as other various biological activities of OA and CBGA derivatives, especially with optimized hydrophobicities at both the alkyl and prenyl side-chain positions of the core skeleton for the discovery of novel drug seeds.