The increasing consumption of coffee in recent years has led to a significant rise in the volume of its waste, highlighting the need to investigate its engineering applicability in construction materials. In this study, coffee waste was added to SCC concrete at volumetric replacement levels of 2.5%, 5%, 7.5%, and 10% of fine aggregates to evaluate its effects on rheological behavior and compressive strength at various curing ages. The mix design was prepared according to EFNARC guidelines, and slump flow, T50, V funnel, J ring, L box, U box, and compressive strength tests were conducted at 7, 28, and 90 days. The results showed that increasing coffee waste reduced the slump flow from 720 mm in the control mix to 560 mm in the C 10% mix, corresponding to a 22.2% decrease. The T50 time increased from 2.8 to 5.2 seconds (an 85.7% rise). The V funnel time increased by up to 130%, and the U box height difference increased by up to 83%. The L box height ratio decreased by approximately 70% in the C 10% mix. However, using 2.5% coffee waste still kept the SCC concrete mix within the acceptable EFNARC limits. The compressive strength results further indicated that coffee waste reduces strength, delays setting, and promotes the formation of weak zones in the concrete. Specifically, replacement levels of 2.5%, 5%, 7.5%, and 10% reduced compressive strength by approximately 9%, 21%, 36%, and 55%, respectively.