Including health outcomes for carers as well as patients in economic evaluations can change the results and conclusions of the analysis. Whilst in many disease areas there can be clear justification for including carers health-related quality of life (HRQL) in health technology assessments (HTAs), we believe that, in general, the perspective of carers is under-represented in HTA. We were interested in the extent, and methods by which, HTA bodies include carers HRQL in economic evaluation. We reviewed guidance from 13 HTA bodies across the world regarding carers HRQL. We examined five interventions, as case studies, assessed by different HTA bodies, and extracted information on whether carers HRQL was included by the manufacturers or assessors in their dossiers of evidence, the data and methods used, and the impact on the results. We developed recommendations to guide analysts on including carers HRQL in economic evaluations. When reviewing the methods guides two bodies recommend including carers HRQL in the base case, two referred to outcomes for all individuals, two preferred to exclude carers, three said it depended on other conditions, and it was unclear for four. Across the five case studies five source studies for carers HRQL and two different modelling approaches were used. Including carers HRQL increased incremental quality-adjusted life-years (QALYs) in 19 of 23 analyses (decreased it in two) there was substantial variation in the magnitude of change. We recommend (1) the inclusion of carers is clearly justified, (2) the use of HRQL data from the population under comparison where possible, (3) the use of data from another disease area or country is clearly justified (and transferability, applicability issues are discussed), (4) the use of external data to derive comparisons for cross-sectional data is justified, (5) assumptions and implications of the modelling approach are explicit, and (6) disaggregated results for patients and carers are presented.