Welti was born in Zurich as the oldest of seven children of Jakob Albert Welti-Furrer (1833-1906), a hauler, and Anna Barbara Furrer.
[1] Part of the French Armée de l'Est was billeted on his grandfather's property in 1871, and watching their activities inspired his later interest in historical scenes.
[1] In 1880, he began a photography apprenticeship[1] with his uncle Oswald Welti (1843-1932) in Lausanne, but stayed with him for only one year, enrolling at the Academy of Fine Arts, Munich in 1882.
[1] He regularly travelled to Switzerland, and after his father's death, Welti assuaged his grief by visiting Innertkirchen and Vättis, where he created numerous pastel nature studies.
Welti's best known work is probably the large fresco Die Landsgemeinde [de], in the meeting room of the Council of States at the Federal Palace, which was commissioned by the Swiss government in 1908.