This paper evaluates whether the relevance of investment properties measured using Level 3 inputs is impacted by the assumptions underpinning the determination of fair values. Evidence is provided of investors generally finding investment property fair values determined with Level 3 inputs to be relevant, and the values are not discounted in market price. However, this is not the case when there is evidence of firms using optimistic assumptions in the determination of fair values. Specifically, there is a material price discount of recognized investment property values as well as fair value gains for these observations. Our research setting of real estate investment firms has several advantages as these firms typically have as their major assets investment properties whose fair value and rental income can be observed from financial reports. This allows investors to easily infer and compare the key valuation assumptions as captured by the capitalization rate. The implication for more general circumstances where valuation assumptions cannot be inferred from financial reports is that detailed disclosures of assumptions are necessary for users to assess the reliability of fair values determined with Level 3 inputs.