Objective: Despite a recommendation for microbiological testing, only 45% of children hospitalized for respiratory infections in our previous data linkage study linked to a microbiological record. We conducted a chart review to validate linked microbiological data. Study Design and Setting: The chart review consisted of children aged <5 years admitted to seven selected hospitals for respiratory infections in Western Australia, 2000–2011. We calculated the proportion of admissions where testing was performed and any pathogens detected. We compared these proportions between the chart review and our previous data linkage study. Poisson regression was used to identify factors predicting the likelihood of microbiological tests in the chart review cohort. Results: From the chart review, 77% of 746 records had a microbiological test performed compared with 46% of 18,687 records from our previous data linkage study. Of those undergoing testing, 66% of the chart review and 64% of data linkage records had ≥1 respiratory pathogen(s) detected. In the chart review cohort, frequency of testing was highest in children admitted to metropolitan hospitals. Conclusion: Validation studies are essential to ensure the quality of linked data. Our previous data linkage study failed to capture all relevant microbiological records. Findings will be used to optimize extraction protocols for future linkage studies.