It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.

S Monocerotis A is a spectroscopic binary system with an eccentric orbit of about 112 years.

[19] It is also an irregular variable star with a range of less than a tenth of a magnitude.

[6] The distance to S Monocerotis and NGC 2264 has been derived in various ways, including dynamical parallax and isochrone fitting.

These consistently give estimates of 700 - 900 parsecs, although this is double the likely distance derived from the Hipparcos parallax measurements.