The vast compressive strength of concrete is attributed to its density, which is achieved through rigorous and thorough compaction. Compaction comes into more prominence in Self-Compacting Concrete (SCC), which gets compacted due to its own weight. Generally, aggregates are the major influential factor for concrete properties, because they exist in quantities varying from 85 to 90% of the total mix volume. This paper presents the findings of the study aimed at comparing rheological and mechanical properties of M30 SCC mix with Indian Standard aggregate gradations (IS 383:1970) and particle packing Bailey aggregate gradations. Specific objectives of the study were to assess the effects of aggregate gradation with three different Nominal Maximum Aggregate Sizes (NMAS), namely 20 mm, 16 mm and 12.5 mm. Rheological properties like Slump-flow test, T500 Slump-flow test, V-funnel test, L-box test, U-box test, Fill-box test were performed and all prepared concrete mixes fulfilled the requirements of the same successfully. Mechanical properties like compressive strength, split tensile strength and flexural strength were determined for all concrete mixes. Results were statistically analyzed to understand the effect of different NMAS and aggregate gradations. Findings indicate that the rheological and mechanical properties were significantly influenced by the different NMAS and aggregate gradations.