The leaves of red trillium are broadly oval to almost diamond-shaped, lending a distinctive appearance. These leaves, technically termed bracts, are arranged in a whorled pattern on the stem and are stalkless to nearly stalkless. They can grow up to 7 inches (18 cm) wide with margins that may curl inward. The leaf surface is smooth and the veining is subtle, enhancing the overall texture. Their unique shape and arrangement are key identifying features.

Red trillium flowers exhibit a distinctive appearance with three petals radiating from a central point. Each bloom measures approximately 2.5 inches (6.35 cm) across and is supported by a recurving stem. The flowers typically have a deep maroon hue with contrasting yellow anthers, though variations in pink, greenish-yellow, and purple are possible. Their odor is notably fetid. Blooms appear between April and June, sometimes taking up to 15 years to emerge from seed.

Red trillium boasts a strikingly smooth, round stem that remains unbranched. It can vary in color, displaying shades of green to reddish hues. The texture of the stem is notably smooth, without any roughness or hair. Typically, the stem's diameter ranges from 0.2 to 0.4 inches (0.5 to 1 cm), supporting the plant's overall structure without branching. This distinctive feature helps in the accurate identification and differentiation of red trillium from other species.

The fruit of red trillium is a 6-parted, berry-like capsule. During peak maturity from July to August, it bears seeds which are most often scattered by the unique assistance of ants. These seeds are enclosed in a textured, fleshy structure that transforms to a bold color as it ripens, attracting its insect dispersers. Typically, the fruit may be found adorning the plant at ground level, visible against the backdrop of its native habitat in North Carolina. Its dimensions and specific coloration are not provided but are in line with what is typical for capsule fruits of the Trillium genus.