In methemoglobinemia, ferrous iron in the hemoglobin is oxidized to a ferric state. Hemoglobin in this state cannot carry oxygen resulting in hypoxemia, which manifests as low peripheral oxygen saturation (SpO2). Bedside co-oximetry can identify this condition. We present here two cases of methemoglobinemia. Our experience with the first case enabled swift diagnosis of the second case. This also enabled us to prepare ourselves better in the second case if worsening of hypoxemia had occurred. Therefore, we learn here that whenever there is low SpO2 with a normal partial pressure of oxygen, methemoglobinemia should be suspected and diagnosis should be confirmed using co-oximetry.