Of the population in the municipality 679 or about 14.5% were born in Cologny and lived there in 2000. There were 1,091 or 23.2% who were born in the same canton, while 560 or 11.9% were born somewhere else in Switzerland, and 1,953 or 41.6% were born outside of Switzerland. In , there were 21 live births to Swiss citizens and 18 births to non-Swiss citizens, and in same time span, there were 28 deaths of Swiss citizens and 6 non-Swiss citizen deaths. Ignoring immigration and emigration, the population of Swiss citizens decreased by 7 while the foreign population increased by 12. There were 19 Swiss men and 22 Swiss women who emigrated from Switzerland. At the same time, there were 43 non-Swiss men and 6 non-Swiss women who immigrated from another country to Switzerland. The total Swiss population change in 2008 (from all sources, including moves across municipal borders) was a decrease of 33 and the non-Swiss population increased by 33 people. This represents a population growth rate of 0.0%. The age distribution of the population () is children and teenagers (0–19 years old) make up 24.3% of the population, while adults (20–64 years old) make up 58.8% and seniors (over 64 years old) make up 16.9%.  , there were 1,853 people who were single and never married in the municipality. There were 2,329 married individuals, 248 widows or widowers and 267 individuals who are divorced.  , there were 1,685 private households in the municipality, and an average of 2.5 persons per household. There were 443 households that consist of only one person and 155 households with five or more people. Out of a total of 1,734 households that answered this question, 25.5% were households made up of just one person and there were 11 adults who lived with their parents. Of the rest of the households, there are 456 married couples without children, 633 married couples with children, and there were 108 single parents with a child or children. There were 34 households that were made up of unrelated people and 49 households that were made up of some sort of institution or another collective housing. The historical population is given in the following chart: The Bibliotheca Bodmeriana (Bodmer Library), which was given as a donation by Martin Bodmer a month before his death on the 26th of February 1971  and Campagne Diodati are listed as Swiss heritage site of national significance.