She's drawn notice for reporting and producing on a wide array of topics, from card-counting in blackjack[1] and her father's car (for the latter, she was the listener-voted favorite in This American Life's 400th-episode competition among the show's producers to see who could develop the best radio story based on an idea pitched by the producer's parents)[2] to race and policing[3] (named to The Atlantic's round-up of "exceptional works of journalism" from 2015),[4] treatment for young, non-offending pedophiles,[5] and school inequality and violence.

[11] Semien and collaborators on the "Harper High School" episode won a Peabody Award, with judges calling the work "vivid, unblinking, poignant and sometimes gut-wrenching”;[12] the Dart Center prize for journalism and trauma (“profoundly moving” and “extraordinarily comprehensive and compassionate"); the Jack R. Howard Award for Radio In-Depth coverage;[13] an Alfred I. duPont-Columbia University Award[14] ("truly immersive, and intercut with lively use of sound[; t]hese elements offered valuable insights");[15] the Fred M. Hechinger Grand Prize for Distinguished Education Reporting from the Education Writers Association;[16] and the Third Coast International Audio Festival's Gold Award for best documentary.

[17] In 2014, Semien, Luke Malone and Ira Glass won Third Coast International Audio Festival's Radio Impact Award[18] for their story about "on the struggles of young, non-offending pedophiles in their teens and early 20s and what they were doing to get treatment.

For the same piece, Semien, Malone and Glass were also finalists for The Society of Professional Journalists' Deadline Club 2015 award for best "Radio or Audio Reporting" and third place in the National Headliners Award for best "Radio stations documentary or public affairs.

"[20] In 2008, Semien was nominated as producer, with This American Life's television team, for the International Documentary Association's award for best continuing series.