In the 2020 census, the population of Marilao, Bulacan, was 254,453 people, with a density of 7,500 inhabitants per square kilometer or 19,000 inhabitants per square mile.
| Year | Pop. | ±% p.a. | Year | Pop. | ±% p.a. | Year | Pop. | ±% p.a. |
|---|---|---|---|---|---|---|---|---|
| 1903 | 3,506 | — | 1970 | 16,128 | +5.76% | 2000 | 101,017 | +8.60% |
| 1918 | 4,202 | +1.21% | 1975 | 21,017 | +5.45% | 2007 | 160,452 | +6.59% |
| 1948 | 5,628 | +1.45% | 1980 | 35,069 | +10.78% | 2010 | 185,624 | +5.45% |
| 1948 | 6,206 | +0.98% | 1990 | 56,361 | +4.86% | 2015 | 221,965 | +3.46% |
| 1960 | 9,206 | +3.34% | 1995 | 68,761 | +3.80% | 2020 | 254,453 | +2.92% |
| Source: Philippine Statistics Authority [16] [11] [17] [18] | ||||||||