This paper investigated reliability of outsourced property valuation services by Financial Institutions (FI) in Lagos State. This is with a view to providing information that would enhance reliability of valuation services provided by estate surveyors and valuers. Primary data used for the study were obtained from the questionnaires administered on 101 financial institutions found within the scope of well-structured financial institutions and accessed through their head offices. A total of 78 questionnaires were retrieved and useable for this study. The data were analyzed using total variance test, t- test and error matrices. The study showed that the level of accuracy of estate surveyors and valuers opinion of values is very low and therefore valuation reports outputs are unreliable; but more reliable than engaging in-house valuation assessment. The study recommends efforts geared towards reduction of margin of errors to make valuation more reliable and objective. Also getting data input of valuation analysis from reliable sources and establishment of centralized data base in every region of the country for valuers use as obtainable in developed countries by the Nigerian Institution of Estate Surveyors and Valuers. This will go a long way in ensuring more reliable valuation opinion which will be helpful for FI in their mortgage transactions and also prevent their investment from going down the drain as a result of wrong advice from Estate Surveyors and Valuers.