Globally, there is wide variation in streptococcal titer upper limits of normal (ULN) for antistreptolysin O (ASO) and anti-deoxyribonuclease B (ADB) used as evidence of recent group A streptococcal (GAS) infection to diagnose acute rheumatic fever (ARF). We audited ASO and ADB titers among individuals with ARF in New Zealand (NZ), and in Australia's Northern Territory (NT). We summarized streptococcal titers by different ARF clinical manifestations, assessed application of locally-recommended serology guidelines where NZ uses high ULN cut-offs, and calculated the proportion of cases fulfilling alternative serologic diagnostic criteria. From January 2013-December 2015, GAS serology results were available for 350 patients diagnosed with ARF in NZ, and 182 patients in NT. Median peak streptococcal titers were similar in both settings. Among NZ cases, 267/350 (76.3%) met NZ serologic diagnostic criteria while 329/350 (94.0%) met Australian criteria. By applying Australian ULN titer cut-off criteria to NZ cases, excluding chorea, ARF definite cases would increase by 17.6% representing 47 cases. ASO and ADB values were similar in these settings. Use of high ULN cut-offs potentially undercounts definite and probable ARF diagnoses. We recommend NZ and other high-burden settings use globally accepted age-specific lower serologic cut-offs to avoid misclassification of ARF.