Inthisstudy,theauthordevelopedamodeltodescribeacademicself-concept(ASC)in scienceandvalidatedaninstrumentforitsmeasurement.UnlikepreviousmodelsofscienceASC, which envisage science as a homogenous single global construct, this model took a multidimen- sionalviewby conceivingscienceself-concept aspossessing distinctivefacetsincluding concep- tualandproceduralelements.Inthefirstpartofthestudy,datawerecollectedfrom1,483students attendingeightsecondaryschoolsinEngland,throughtheuseofanewlydevisedSecondarySelf- Concept ScienceInstrument,and structural equation modeling was employed totest and validate a model. In the second part of the study, the data were analysed within the new self-concept framework to examine learners’ ASC profiles across the domains of science, with particular attention paid to age- and gender-related differences. The study found that the proposed science self-concept model exhibited robust measures of fit and construct validity, which were shown to be invariant across gender and age subgroups. The self-concept profiles were heterogeneous in nature with the component relating to self-concept in physics, being surprisingly positive in comparison to other aspects of science. This outcome is in stark contrast to data reported elsewhere and raises important issues about the nature of young learners’self-conceptions about science.Thepaperconcludeswithananalysisofthepotentialutilityoftheself-conceptmeasure- ment instrument as a pedagogical device for science educators and learners of science.