<p>Pile foundations are integral to ensuring the stability and support of diverse structures, ranging from buildings to offshore platforms. Among various pile configurations, under-reamed piles have gained prominence due to their potential to enhance load-bearing capacity, especially in challenging soil conditions. This study presents a comprehensive investigation into the uplift capacity of different under-reamed pile configurations in saturated marine clay and clayey sand. Laboratory model pile load tests were carried out on single and double under-reamed piles, half-bulb under-reamed piles, and normal piles in these soil types. Additionally, various methodologies for determining failure loads and safe capacity were compared, to check their reliability for under-reamed piles. The findings revealed that single under-reamed piles with a 45° bulb angle and double under-reamed piles with a bulb spacing of 1.5 times the bulb diameter exhibited superior uplift resistance. Also, the double-tangent method of failure load estimation was found to be comparable with the failure load taken as the load corresponding to an uplift of 7.5% of the bulb diameter. Notably, half-bulb under-reamed piles demonstrated economic viability by combining impressive uplift capacity with material efficiency across both soil conditions.</p>