<p>Galaxy clusters represent some of the most extreme environments in the Universe. They are ideal locations to study the impact of an extreme environment on the evolution of the Stellar Mass Function (SMF), which describes the statistical distribution of galaxies as a function of their stellar masses. In this work, we examine how the SMF of galaxies depends on factors such as the surrounding environments, whether they reside in isolated fields or clusters. We use the 9-band photometric galaxy data of the G9 patch from the Kilo Degree Survey (optical) and the VISTA Kilo-Degree Infrared Galaxy Survey (infrared), containing around 3.7 million galaxies, overlapping with the cluster catalog provided by the eROSITA Final Equatorial Depth Surveys (eFEDS). After applying appropriate selection criteria, we have 105 eFEDS clusters within the redshift range 0.385–0.8, covering <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\sim 46\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∼</mo> <mn>46</mn> </mrow> </math></EquationSource> </InlineEquation> square degrees. The large, continuous overlap of the surveys allows us to examine the SMF of the cluster galaxies within the cluster-centric radial bins up to <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(5R_{500}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>5</mn> <msub> <mi>R</mi> <mn>500</mn> </msub> </mrow> </math></EquationSource> </InlineEquation>. We find a clear detection of the cluster galaxy SMF up to <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(2R_{500}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <msub> <mi>R</mi> <mn>500</mn> </msub> </mrow> </math></EquationSource> </InlineEquation> beyond which it’s consistent with the background. We divide the cluster sample into redshift, mass, and X-ray luminosity bins to examine their impact on the SMF. The SMF of cluster galaxies for the high-mass clusters shows a decline at low stellar masses (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(M_*\lesssim 2\times 10^{10}M_\odot \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>M</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>≲</mo> <mn>2</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>10</mn> </msup> <msub> <mi>M</mi> <mo>⊙</mo> </msub> </mrow> </math></EquationSource> </InlineEquation>) within <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(0-0.5R_{500}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>-</mo> <mn>0.5</mn> <msub> <mi>R</mi> <mn>500</mn> </msub> </mrow> </math></EquationSource> </InlineEquation>, as compared to a flat SMF for the low-mass clusters, suggesting the low-mass galaxies grow over time before reaching the cluster center. Additionally, we find a flatter SMF for the low redshift bin within <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(0.5R_{500}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.5</mn> <msub> <mi>R</mi> <mn>500</mn> </msub> </mrow> </math></EquationSource> </InlineEquation> at stellar masses <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(M_*&lt; 10^{10}M_\odot \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>M</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>&lt;</mo> <msup> <mn>10</mn> <mn>10</mn> </msup> <msub> <mi>M</mi> <mo>⊙</mo> </msub> </mrow> </math></EquationSource> </InlineEquation>. We also examined the effect of cluster ellipticity on the cluster galaxy SMF; however do not find statistically significant differences between the high and the low ellipticity clusters.</p>