Fossil and Recent shells of Turritella leucostoma (Valenciennes, 1832) are common in the Northern Gulf of California and, during winter months, living specimens can be found populating tidal flat environments. At San Felipe, Baja California, Mexico, T. leucostoma preferentially inhabit the sediment near the base of tidal channels and the low tide beach, where a total of 45 live specimens were gathered and documented. Most specimens were found in feeding position with the aperture exposed at the sediment surface and the apex pointed down at a low angle into the sediment. They act as predominantly stationary semi-infaunal active suspension feeders. Actively moving specimens were encountered during day and night low tides. The size distribution of the shells is narrow and no juveniles occur on the San Felipe tidal flat. Analysis of δ¹⁸O performed on three shells shows variations of up to 3.4‰ attributable to seasonal changes in water temperature, and indicates longevity of 1.5–2 years and relatively constant growth rates. The carbon isotopic composition of the analyzed shells suggests that the individuals moved from a deeper environment to a tidal flat environment after their first year of life where they may have been subject to a change in diet and ambient dissolved inorganic carbon composition and/or began to incorporate more isotopically-light respiratory carbon into the shell.