Saint-Blaise has a population (as of December 2018) of 3,212.
 As of 2008, 19.8% of the population are resident foreign nationals.
 Over the last 10 years (2000–2010) the population has changed at a rate of 0.4%.
 It has changed at a rate of -4.6% due to migration and at a rate of 3.1% due to births and deaths.

Most of the population (as of 2000) speaks French (2,573 or 82.5%) as their first language, German is the second most common (243 or 7.8%) and Italian is the third (109 or 3.5%).
 There are 3 people who speak Romansh.

As of 2008, the population was 49.1% male and 50.9% female.
 The population was made up of 1,211 Swiss men (38.6% of the population) and 329 (10.5%) non-Swiss men.
 There were 1,348 Swiss women (42.9%) and 251 (8.0%) non-Swiss women.
 Of the population in the municipality, 606 or about 19.4% were born in Saint-Blaise and lived there in 2000.
 There were 932 or 29.9% who were born in the same canton, while 769 or 24.7% were born somewhere else in Switzerland, and 722 or 23.2% were born outside of Switzerland.

As of 2000, children and teenagers (0–19 years old) make up 21.7% of the population, while adults (20–64 years old) make up 61.1% and seniors (over 64 years old) make up 17.3%.

As of 2000, there were 1,132 people who were single and never married in the municipality.
 There were 1,616 married individuals, 184 widows or widowers and 185 individuals who are divorced.

As of 2000, there were 1,337 private households in the municipality, and an average of 2.3 persons per household.
 There were 405 households that consist of only one person and 55 households with five or more people.
 In 2000, a total of 1,304 apartments (91.1% of the total) were permanently occupied, while 100 apartments (7.0%) were seasonally occupied and 27 apartments (1.9%) were empty.
 The vacancy rate for the municipality, in 2010, was 0.41%.

The historical population is given in the following chart:
Saint-Blaise has a population (as of December 2018) of 3,212.  As of 2008, 19.8% of the population are resident foreign nationals.  Over the last 10 years (2000–2010) the population has changed at a rate of 0.4%.  It has changed at a rate of -4.6% due to migration and at a rate of 3.1% due to births and deaths.
Most of the population (as of 2000) speaks French (2,573 or 82.5%) as their first language, German is the second most common (243 or 7.8%) and Italian is the third (109 or 3.5%).  There are 3 people who speak Romansh.
As of 2008, the population was 49.1% male and 50.9% female.  The population was made up of 1,211 Swiss men (38.6% of the population) and 329 (10.5%) non-Swiss men.  There were 1,348 Swiss women (42.9%) and 251 (8.0%) non-Swiss women.  Of the population in the municipality, 606 or about 19.4% were born in Saint-Blaise and lived there in 2000.  There were 932 or 29.9% who were born in the same canton, while 769 or 24.7% were born somewhere else in Switzerland, and 722 or 23.2% were born outside of Switzerland.
As of 2000, children and teenagers (0–19 years old) make up 21.7% of the population, while adults (20–64 years old) make up 61.1% and seniors (over 64 years old) make up 17.3%.
As of 2000, there were 1,132 people who were single and never married in the municipality.  There were 1,616 married individuals, 184 widows or widowers and 185 individuals who are divorced.
As of 2000, there were 1,337 private households in the municipality, and an average of 2.3 persons per household.  There were 405 households that consist of only one person and 55 households with five or more people.  In 2000, a total of 1,304 apartments (91.1% of the total) were permanently occupied, while 100 apartments (7.0%) were seasonally occupied and 27 apartments (1.9%) were empty.  The vacancy rate for the municipality, in 2010, was 0.41%.
The historical population is given in the following chart:
Saint-Blaise, Switzerland