A total of 16.7 percent of Spain's 10.6 million people aged over 60 are living on less than half the national income of $26,856 (€19,810), the Global AgeWatch Index 2013 shows.
Overall, Spain came in at 22nd place in the survey which looked at the living conditions of older people in 91 countries worldwide.
The study released on Tuesday looked at income security, health security, and employment and education levels to come up with its results.
Researchers also looked at factors such as physical safety, civic freedom and access to public transport.
For income security, Spain ranked 31st with 89.9 percent of people aged 65 and over receiving a pension and people over 60 having 86 percent of the average income and consumption of the rest of the population.
Spain achieved far lower results for employment and education, with the country ranking 50th in the AgeWatch survey.
Only 43.6 percent of people aged 55 to 64 were found to be working while just 43.4 percent of people in this age group had secondary or higher education.
Where Spain ranked well was in the Enabling societies and environment category.
The country took 14th place for factors including social connections, with 92 percent of people over 50 having relatives or friends they can count on when in trouble.
The index "challenges countries in every part of the world to raise their sights as to what is possible", said Professor Sir Richard Jolly, creator of the Human Development Index.
"The Index will enrich the debate on sustainable development by looking beyond the relationship between investment in ageing and economic growth to how we can support people's capabilities and choices as they age — for the benefit of all ages."
The release of the Global AgeWatch Index also comes in the wake of the proposal of tough new pension reforms in Spain.
These will see pension payments climb by a minimum of just 0.25 percent every year, or a long way below expected inflation.
The reforms are designed to rein in Spain's huge public debt with savings of €33 billion euros planned over the next decade.