This study evaluated the effects of hemp leaf (HL), hemp seed (HS), and pelleted hempseed meal (HP) on rumen fermentation parameters, and feed value using the in vitro gas production technique. Chemical analyses showed highly significant differences between the three hemp-derived feed materials (P < 0.01). Except for microbial protein (MP; P > 0.05), all evaluated in vitro fermentation parameters, including gas production (GP), methane production (ml and %), truly digested dry matter (TDDM), partitioning factor (PF), and microbial protein synthesis efficiency (MPSE) differed significantly between the groups (P < 0.01). Feed value was assessed based on organic matter digestibility (OMD), neutral detergent fibre digestibility (NDFD), metabolizable energy (ME), net energy for lactation (NEL), dry matter digestibility (DMD), dry matter intake (DMI), relative feed value (RFV), and relative forage quality (RFQ). Hemp seed and hempseed pelleted meal showed similar values for most evaluated parameters, differing only in OMD, whereas hemp leaf had the highest values for most fermentation and feed quality parameters. Differences among the groups were significant for all feed value indices (P < 0.01). In conclusion, HL, HS, and HP show potential as alternative energy and protein sources in ruminant diets. However, further in vivo studies are needed to confirm their effects on animal performance and health.