In the last few decades, macrolide-resistant Mycoplasma pneumoniae (MRMP) has been increasing in proportion. This study aimed to evaluate the treatment outcomes of children with lobar or segmental MP pneumonia unresponsive to the initial 3–5-day macrolide therapy, who then switched to either a non-macrolide, macrolide + steroid, or a non-macrolide + steroid regimen, according to the 2019 KSPID and KAPARD guideline during the 2019–2020 Mycoplasma epidemic in South Korea. A total of 190 patients <18 years old were admitted during the study period for MP lobar or segmental pneumonia, and 16.8% (n = 32/190) were responsive to the initial macrolide monotherapy, whereas 83.2% (158/190) were refractory. The median age of the patients was 7 (interquartile range [IQR], 5–9) years old and 46.2% (n = 73/158) were male. The overall treatment success rates of non-macrolide, macrolide + steroid, and non-macrolide + steroid groups were 46.2%, 80.8%, and 100.0%, respectively. Patients in the non-macrolide + steroid group had the shortest fever duration after a regimen change of 1 (IQR, 0–3) day compared with patients in the non-macrolide group and macrolide + steroid group; 2 (IQR, 1–4) days and 2 (IQR, 1–3.3) days (p = 0.004), respectively. Follow-up CRP (ß, 0.169; CI, 0.050–0.287; p = 0.006), macrolide + steroid therapy (ß, −1.694; CI, −2.463–−0.925; p < 0.001), and non-macrolide+ steroid therapy (ß, −2.224; CI, −3.321–−1.127; p < 0.001) were shown to be significantly associated with the duration of fever after admission. To conclude, in patients with severe MP pneumonia that failed to respond to the initial macrolide therapy, a non-macrolide + steroid had the highest treatment success rate and a shorter duration of fever.