Trachselwald has a population () of . , 3.7% of the population are resident foreign nationals. Between the last 2 years (2010-2012) the population changed at a rate of -4.1%. Migration accounted for -2.0%, while births and deaths accounted for 0.8%. Most of the population () speaks
German (1,086 or 98.7%) as their first language,
French and
Italian both have only 2 speakers in the municipality. Of the population in the municipality, 521 or about 47.4% were born in Trachselwald and lived there in 2000. There were 436 or 39.6% who were born in the same canton, while 91 or 8.3% were born somewhere else in Switzerland, and 26 or 2.4% were born outside of Switzerland. , there were 99 households that consist of only one person and 48 households with five or more people. , a total of 355 apartments (87.7% of the total) were permanently occupied, while 26 apartments (6.4%) were seasonally occupied and 24 apartments (5.9%) were empty. The vacancy rate for the municipality, , was 2.2%. In 2012, single family homes made up 31.5% of the total housing in the municipality. The historical population is given in the following chart: Colors= id:lightgrey value:gray(0.9) id:darkgrey value:gray(0.8) ImageSize = width: auto height:200 barincrement:45 PlotArea = top:20 left:40 bottom:20 right:35 AlignBars = justify DateFormat = x.y Period = from:0 till:1800 TimeAxis = orientation:vertical AlignBars = justify ScaleMajor = gridcolor:darkgrey increment:400 start:0 ScaleMinor = gridcolor:lightgrey increment:80 start:0 PlotData= color:yellowgreen width: 35 mark:(line,white) align:center bar:1764 from:start till:970 text:"970" bar:1850 from:start till:1717 text:"1,717" bar:1860 from:start till:1672 text:"1,672" bar:1870 from:start till:1670 text:"1,670" bar:1880 from:start till:1604 text:"1,604" bar:1888 from:start till:1554 text:"1,554" bar:1900 from:start till:1473 text:"1,473" bar:1910 from:start till:1531 text:"1,531" bar:1920 from:start till:1458 text:"1,458" bar:1930 from:start till:1387 text:"1,387" bar:1941 from:start till:1335 text:"1,335" bar:1950 from:start till:1393 text:"1,393" bar:1960 from:start till:1269 text:"1,269" bar:1970 from:start till:1199 text:"1,199" bar:1980 from:start till:1054 text:"1,054" bar:1990 from:start till:1046 text:"1,046" bar:2000 from:start till:1100 text:"1,100" bar:2010 from:start till:1015 text:"1,015" ==Economy==