Due to the hierarchical structure, fibre reinforced polymer composites exhibits randomness at multiple scales, for example, the constituent material properties and the layer thickness could be random at micro and macroscale, respectively. In addition, some of these uncertainties may not have sufficient probability information to be precisely described as random variables, and they are treated as interval variables. This study, proposes a novel framework to estimate the boundary of mechanical properties of fibre reinforced polymer composites with hybrid and internal uncertainties. Within this framework, the random and interval uncertainties are expressed in terms of Hermite and Chebyshev polynomials, respectively, within the PCE-based surrogate model. By doing so, the multiscale analysis is embedded in the hybrid surrogate model to realize the multiscale random-interval uncertainty analysis. Numerical examples are carried out to demonstrate the feasibility of the proposed method, and results show that this method can accurately obtain the upper and lower bounds of structural responses, e.g. failure probability, of FRP composite structures. © 2022 Elsevier Ltd