We report the implementation of a pediatric home spirometry program at our institution. A respiratory therapist provided either a virtual or an in-person initiation visit that included a coached spirometry session. Families were instructed to perform daily uncoached spirometry sessions for 5 days. The program’s quality assurance component was deemed not to be human research by the local IRB. In total, 52 subjects completed an initiation visit (34 with at least 3 additional uncoached spirometry sessions). The clinic spirometry and coached (same-day) sessions and uncoached (same-week) sessions were completed by 12 and 17 subjects, respectively. The median (99% CI) coefficients of variation for FEV1% of the uncoached maneuvers were 3.5% (2.9–5.9%). The median (IQR) FEV1% and FEV1 (mL) absolute differences between coached and uncoached home spirometry were −2% (−4 and +3%) and −25 mL (−93 and +93 mL), respectively. The median (IQR) absolute differences in FEV1% and FEV1 (mL) between coached or uncoached home spirometry and clinic spirometry were −6% (−10 and −2%) and −155 mL (−275 and −88 mL), and −4% (−10 and +5%), and −110 mL (−280 and +9 mL), respectively. Differences in absolute FEV1 (L) and FEV1% were found among different modalities of spirometry performed by people with cystic fibrosis. Understanding the variability of uncoached home spirometry and the differences among coached and uncoached home spirometry, hospital and coached home spirometry, and hospital and uncoached home spirometry for any given individual is crucial to effectively utilize this tool in clinical care.