<p>We perform a complete calculation of the next-to-next-to-leading order (NNLO) electroweak fermionic corrections to fermion-pair production processes, where “fermionic” refers to contributions with closed fermion loops. We do this via a semi-numerical technique that uses dispersion relations for the fermion sub-loop in two-loop box and vertex diagrams and dispersion relations and Feynman parameters for vertex diagrams with fermionic triangle sub-loops. UV and IR divergences are treated with suitable subtraction terms. We present numerical results for the cross-sections of <InlineEquation ID="IEq1"> <EquationSource Format="MATHML"><math display="inline"> <msup> <mi>e</mi> <mo>+</mo> </msup> <msup> <mi>e</mi> <mo>−</mo> </msup> <mo>→</mo> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msup> <mi>μ</mi> <mo>−</mo> </msup> <mo>/</mo> <mi>u</mi> <mover accent="true"> <mi>u</mi> <mo stretchy="true">¯</mo> </mover> <mo>/</mo> <mi>d</mi> <mover accent="true"> <mi>d</mi> <mo stretchy="true">¯</mo> </mover> </math></EquationSource> <EquationSource Format="TEX">\( {e}^{+}{e}^{-}\to {\mu}^{+}{\mu}^{-}/u\overline{u}/d\overline{d} \)</EquationSource> </InlineEquation> and differential distributions at representative center-of-mass energies. The NNLO corrections are found to modify the NLO cross-section on the order of 1%.</p>