Carlo Ancelotti's side have enjoyed a stellar last 12 months that has also seen them lift the UEFA Champions League, Copa del Rey and UEFA Super Cup.
Victory on Saturday extended Real's remarkable winning run to 22 matches in all competitions as the Spanish giants continue to sweep all before them on all fronts.
Sergio Ramos - who had been a doubt for the game after picking up a knock in the 4-0 semi-final win over Cruz Azul - headed in Real's first goal from Toni Kroos' corner in the 37th minute.
Gareth Bale benefited from a mistake by San Lorenzo goalkeeper Sebastian Torrico shortly after half-time as the Welshman continued his fine record in finals, having also netted in the Champions League and Copa showpieces this year.
Argentine Primera Division outfit San Lorenzo rarely threatened Iker Casillas' goal, as Real were able to comfortably see out the win and earn themselves a fourth trophy in eight months.
Real showed one alteration from their semi-final as James Rodriguez came back in for Asier Illarramendi after he recovered from a calf problem, while San Lorenzo were unchanged from their 2-1 extra-time win over Auckland City.
Ancelotti's men made a bright start and came close to opening the scoring in the first minute when Karim Benzema just failed to get a touch on Cristiano Ronaldo's low ball across the box.
The opening exchanges were scrappy, with San Lorenzo continually breaking up play with a series of fouls designed to upset the European champions' rhythm.
Guatemalan referee Walter Lopez struggled to curb fraying tempers, dishing out two yellow cards to each side in the opening half an hour.
After two Ronaldo free-kicks passed without alarm for San Lorenzo, Benzema brought a comfortable save out of Torrico with a low shot that lacked power.
Torrico saved at his near post from Bale soon afterwards, but San Lorenzo's respite was short-lived as, from the resulting corner, Ramos got up highest to nod in Kroos' delivery.
As the half drew to a close, there was one moment of concern for Real as left-back Marcelo had to be withdrawn following a knock, with Fabio Coentrao coming on in his place.
Six minutes after the interval, the Spanish giants took a firm grip on proceedings when Isco played in Bale, whose weak shot squeezed under the body of Torrico and trickled over the line.
Bale almost added a third in the 64th minute, but his attempted cross from the right clipped the crossbar and bounced behind to safety.
Ancelotti's side continued to dominate and Benzema sent a close-range volley wide of the upright after getting on the end of Bale's delightful centre with the outside of his left boot.
Enzo Kalinski and Juan Mercier did bring smart stops out of Casillas in the final 10 minutes, but Real’s lead never looked in any serious danger as they finished 2014 on another high note, ahead of a two-week break before their return to La Liga action on January 4.
