Background Length of stay (LOS) is an essential metric for hospital efficiency, patient outcomes and satisfaction. Studies indicate hospital pharmacy interventions positively affect LOS and other outcomes, yet results vary due to study differences. No systematic review or meta-analysis has been conducted on this topic; thus, the aim of this study is to systematically assess the effect of interventions on LOS. Methods This review will conduct a systematic search across MEDLINE, EMBASE, Cochrane Trials, Cochrane Reviews and the Cumulative Index to Nursing and Allied Health Literature to identify pertinent studies. An expert librarian will craft the search strategy, ensuring our review adheres to standard guidelines. We will use Covidence, a specialized systematic review management software, to optimize data management, the selection process and data extraction. A dedicated team of reviewers will independently evaluate titles and abstracts in duplicate, progressing to full-text examination of articles, to determine inclusion in our review and analysis. Data will be extracted by one reviewer, with independent data extraction by a second reviewer in a proportion of papers, and checking for consistency by a third. A template in Covidence will guide extraction of study, setting, participant, intervention and outcome characteristics and findings. The findings will be described narratively, and if possible given the methodological and statistical heterogeneity, meta-analysis will be undertaken. Discussion Considering the inconsistency of previous studies, this systematic review aims to clarify the potential impact of hospital pharmacy interventions on LOS. It will expand and reinforce existing knowledge, and provide detail about which intervention types have the most impact on LOS.