Background: Over the past decade, the financial crisis has affected harshly the household income of Greek people. This study aimed to investigate whether the effect of the financial crisis on food spending has affected the dietary habits in the family environment. Methods: Under a cross-sectional study conducted during 2014-2016, 1145 children and their parents completed questionnaires examining socio-economic and dietary characteristics. The MedDietScore and the KIDMED Score were used to assess parental and childhood adherence to the Mediterranean diet, respectively. Results: The parents who reported that the financial crisis has affected food spending used to consume weekly fewer fruits (3.26 ± 0.94 vs. 3.41 ± 0.90, P = 0.016), carbohydrate foods (3.16 ± 0.57 vs. 2.99 ± 0.55, P < 0.001) and legumes (3.28 ± 0.76 vs. 3.14 ± 0.67, P = 0.001) and more nutrient-poor/energy-dense foods (2.55 ± 0.98 vs. 2.20 ± 0.82, P < 0.001) compared with non-affected parents. Their children showed a decreased weekly consumption of vegetables (2.82 ± 0.90 vs. 2.97 ± 0.98, P = 0.019) and increased weekly consumption of nutrient-poor/energy-dense foods (2.38 ± 0.97 vs. 2.19 ± 0.80, P < 0.001). The affected parents had a lower MedDietScore than non-affected parents (25.76 ± 8.10 vs. 27.03 ± 8.11, P = 0.034). No difference was revealed on the KIDMED Score (P = 0.294). Conclusions: The constrained food spending due to financial crisis has an independent and inverse impact on parent's diet quality while keeping unaffected preadolescent's diet quality. This finding highlights the role of parents as a protective 'wall' against the deterioration of their children's diet quality. The modification on the prices of healthy food and the provision of food aid particularly in economically disadvantaged households is underlined.