Glycosmis pentaphylla (Retz.) DC (Rutaceae) has been traditionally considered as anti-cancer and anti-inflammatory medicine. However, active compounds of sulphur-containing amides remain largely unknown. In the present work, eighteen previously undescribed sulphur-containing amides (1–18) and three known analogues (19–21) were isolated from the leaves of G. pentaphylla. Their structures were elucidated by NMR spectroscopy and mass spectrometry. All isolated prenylated sulphur-containing amides were evaluated for their anti-inflammatory properties together with antiproliferative activities in vivo. Prenylated sulphur-containing amides exhibited significant inhibitory effects against nitric oxide (NO) production stimulated by lipopolysaccharide in mouse macrophage RAW 264.7 cells with the IC50 values ranging from 0.16 ± 0.10 to 16.74 ± 2.81 μM. Meanwhile, sulphur-containing amides also exhibited considerable antiproliferative activities against HepG2 cell line with IC50 values ranging from 7.47 ± 0.91 to 16.23 ± 0.80 μM. These findings enrich and improve the research on the structural diversity and biological activity of sulphur-containing amides and provide phytochemical and pharmacological evidence for the further development and utilization of the leaves of G. pentaphylla in pharmaceutical industry.