Sydney C. Jelinek was born in Wilmington, DE, the son of Emmanuel and Mary (Klein) Jelinek. He graduated from Central High School in Philadelphia in 1917 and received his B.S. in Architecture from the University of Pennsylvania in 1924. From 1924 to 1932 he was employed by William H. Lee; from 1934 to 1937 he was in the office of Simon & Simon; and from 1944 to 1946 he worked for Thalheimer & Weitz. While he did not formally establish his own office in Philadelphia until 1942, Jelinek is listed as the architect on building permits for several properties in the Philadelphia area as early as 1926. In his private practice Jelinek designed a number of factory buildings and apartment houses. He retired from practice in 1976.

Sydney C. Jelinek joined the national AIA in 1945 and was also a member of the Philadelphia Chapter. He served as an assistant in architecture at the University of Pennsylvania from 1920 to 1922 and won a bronze medal in the 1924 Olympics held in Paris, France, in the four-man rowing event. Locally, Jelinek was also a member of the Bachelors' Barge Club and served on the Philadelphia City Planning Commission from 1933 to 1934.

Written by Sandra L. Tatman.