In this work, the annual behavior and cross-correlation between three different solar-ionospheric indices were evaluated: Smoothed Sunspot Number (SSN), Ionospheric T-Index (T-index), and Solar Flux (F10.7 cm) index during solar cycles 23 and 24. The annual behavior for the three tested indices of the maximum and minimum years of the two solar cycles was studied. The correlative conducts between the studied indices were evaluated for the studied periods (1996-2008) and (2008-2019) of the 23rd and 24th solar cycles. The annual correlation between the studied indices was represented by the linear regression equation. The suggested mutual correlation equation gave a good agreement with the observed annual average values of the tested indices. The statistical calculation results of the calculated datasets of the tested indices showed very good results for all statistical parameters. The evaluation of the annual correlations between tested solar-ionospheric indices showed that the tested indices are mutually and linearly correlated to each other and can be predicted reciprocally depending on the suggested mathematical correlated equations.