The effectiveness of counselling patients on antibacterial rational use by pharmacists depends on their knowledge and attitude to counselling.This study evaluated the effect of intervention training on pharmacists’ antibacterial therapy knowledge and attitude to counselling. It was a cross-sectional questionnaire-based study among all the pharmacists (n=45) responsible for patients’ antibacterial counselling in seventeen government secondary health care institutions in Ogun state of Nigeria between November 2017 and May 2018. Identified deficits were addressed through intervention and re-assessment was carried out after a month. Twenty four (53.3%) were females. Twenty one (46.7%) had hospital pharmacy experience of over 10 years and mean year of experience was 10.7±6.7. Sixteen (35.6%) and 36 (80.0%) believed that antibacterial resistance may be prevented by taking antibacterial medication at regular intervals at the baseline and post intervention phases respectively. Thirty three (73.3%) and 44 (97.8%) had the opinion that pharmacists and patients are active participants in effective antibacterial counselling at the two phases respectively. Twenty eight (62.2%) and 44 (97.8%) had scores ≥ 70.0% signifying good knowledge pre and post intervention respectively. Disclosure of antibacterial identity to patients was believed to be necessary by thirty six (80.0%) and 43 (95.6%) while 27 (60.0%) and 43 (95.6%) exhibited positive attitude to antibacterial counselling at the two phases respectively. There was significant improvement in antibacterial knowledge and attitude to counselling (p < 0.001) post intervention. Regular antibacterial therapy and counselling training is hereby recommended for pharmacists.