| Place Name | Holtsville |
| Place Type | Census Designated Place |
| ZIP Code(s) | 11742 |
| County | Suffolk County |
| Area Code(s) | 631,934 |
| Timezone | Eastern Daylight Time (EDT) |
| Population (2022) | 19,689 |
| Population Growth Rate (2010-19) | -3.94% |
| Majority Ethnicity | White 80.07% |
| Metro/Micro Stats Area | New York-Newark-Jersey City, NY-NJ-PA |
| US Congressional District(s) | New York 1st |
| State Assembly Districts | 3,5 |
| State Senate Districts | 3 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 80.07% |
| African American | 5.29% |
| Hispanic | 0% |
| Asian | 3.44% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 11.2% |