Gut development and organ integrity are central to nutrient utilization, immune competence, and overall performance in broiler chickens. With restrictions on antibiotic growth promoters, phytogenic feed additives have emerged as natural strategies to enhance gut function while ensuring food safety. Piper guineense, a West African spice rich in alkaloids and essential oils, has demonstrated antimicrobial and growth-promoting potential, yet its effects on intestinal morphometry and organ histology in poultry remain poorly studied. This study was therefore conducted to evaluate the influence of dietary P. guineense leaf and seed (2:1 ratio) on intestinal morphometry and organ (liver and kidney) histology of broiler chickens. A total of 288-day-old broiler chicks were randomly assigned to four dietary treatments containing 0%, 0.5%, 1.0%, or 1.5% P. guineense and reared on deep litter for 6 weeks. At the end of the trial, two birds per replicate were humanely sacrificed. Intestinal segments (duodenum, jejunum, ileum, pancreas, colon, and caecum) were excised and their length weight were measured, while liver and kidney tissues were fixed in 10% buffered formalin, processed using standard paraffin embedding, sectioned at 5 µm, stained with hematoxylin and eosin, and examined under light microscopy. Results revealed that birds fed 1.0% inclusion exhibited significantly (p < 0.05) longer colons and heavier colons and caecums, suggesting enhanced hindgut development and fermentation capacity, with no detectable alterations in liver and kidney tissues. Conversely, birds fed 1.5% inclusion showed reduced jejunal and ileal weights, increased duodenal length, and histopathological lesions in the liver and kidney, including hepatocellular degeneration and mild renal tubular damage. In conclusion, moderate inclusion (1.0%) of P. guineense supports beneficial gut development without compromising organ health, whereas excessive inclusion (1.5%) may impair small intestinal growth and induce metabolic organ damage. These findings highlight the dual efficacy and safety considerations of P. guineense as a phytogenic additive and underscore the importance of dose optimization in broiler nutrition.