This instrumental study is the Spanish adaptation and validation of the Job Insecurity Scale in its 8-item version (JIS-8). This is one of the reference tests in this field and it also allows the distinction between affect and cognition in quantitative job insecurity to be tested.The JIS-8 was carried out on a Spanish sample with 592 participants (186 men, 406 women; Mean age = 36.68), together with mental health and job satisfaction tests. An exploratory factor analysis and confirmatory factor analysis were carried out, and the relationship between the scale and other variables was examined.The Spanish validation shows good construct validity, internal consistency and a Cronbach a = .88, higher than the value obtained in the validation of the original instrument. The analysis shows the consequences of job insecurity on workers’ mental health, as well as on their job satisfaction. The exploratory factor analysis as well as the confirmatory analysis, in which a one-dimensional and a two-dimensional model were tested, maintain the presence of two factors: the cognitive and the affective dimensions.The results underpin the fact that the test is appropriate for application to people in active employment in the Spanish population.