Interstitial lung disease (ILD) is a term used to describe a heterogeneous group of lung disorders with characteristic clinical and imaging features. Patients with ILD are at an increased risk of developing non-small cell lung cancer and are frequently medically comorbid often precluding operative management. In this scenario, radiotherapy (RT) is generally recommended however ILD is known to increase the risk of RT-related toxicity. Recommendations for treatment with appropriately individualized risks and benefits are thus dependent on integration of patient-, ILD-, and cancer-specific factors. We aim to provide an overview of ILD for the thoracic radiation oncologist, an assessment of risk of thoracic RT in ILD patients, and evidence based recommendations for treatment for a variety of clinical scenarios.