Avian pathogenic Escherichia coli (APEC) strains are causative agents of colibacillosis, an infectious disease that inflicts substantial commercial losses on poultry farms worldwide. The growing resistance of E. coli to antibiotics necessitates the search for alternative approaches to treat and prevent avian colibacillosis, phage therapy being one of them. This review covers 25 years of experimental studies (PubMed, Google Scholar) that examine various aspects of phage therapy with a particular focus on comparing different administration routes (with drinking water; injected orally, intratracheally, or intramuscularly; sprayed as aerosols). It also compares various techniques of introducing phage preparations to avian embryos (injections in ovo). The review describes such aspects as the general efficacy of the administration routes and their specific advantages (e. g., convenience of the aerosol-spraying technique for treating large flocks). It focuses on the advantages of multi-phage cocktails over single-phage preparations, combined antibiotic/phage therapy during colibacillosis epidemics, and administering phage preparations in nanocapsules. The review also discusses the possible interference of the avian immune system with the delivery of phage particles to the infected organs and the importance of phage selection for the success of the therapy.