Objective: This study aims to assess the accuracy of pulmonary nodule detection via MRI compared to the gold standard, CT, in patients with extrathoracic cancer. Materials and Methods: MRI of the chest was performed on oncological patients for staging extrathoracic cancer and subsequently compared to their CT. Only the largest nodule was considered in patients with multiple nodules. Nodule size and malignancy were recorded for each modality, as well as the presence of interstitial lung disease (ILD), adenopathy, cardiomegaly, pleural effusion, pericardial effusion, and vertebral fracture. All cases were read by two thoracic radiologists and any discrepancies were resolved by discussion. Results: A total of 154 patients with nodules were identified from 241 participants (mean age: 59 years [18–95]). Average nodule diameter was 11.5 mm (range: 3.9–29.1 mm; SD: 8.1 mm). MRI detected all nodules greater than 5 mm. Malignancy was detected in 37 nodules. The sensitivity, specificity, and accuracy values of MRI for all nodules were 93.51%, 100%, and 95.85%, respectively. For ground-glass nodules (n = 11), the values were 43.6%, 100%, and 65.0%, respectively. When compared to CT, long-axis diameter measured by MRI was underestimated by 9 ± 2.3% (p < 0.001). There was a strong correlation between measurements of CT and MRI (κ = 0.70–1.00). Furthermore, MRI accurately detected the presence of adenopathy (97.1%), cardiomegaly (99.17%), pleural effusion (98.34%), pericardial effusion (100%), and vertebral fracture (99.6%). Conclusions: These findings suggest that lung MRI accurately detects pulmonary nodules and other thoracic pathologies commonly observed in oncological patients. Lung MRI may serve as a substitute to CT for oncological patients undergoing routine extrathoracic surveillance, thereby decreasing radiation exposure.