Atletico Madrid's victory over Levante earlier in the afternoon had closed the gap to two points, but Barcelona made it six straight La Liga wins with a three-goal success over Eibar to move clear at the summit once again.
Gerard Pique's flicked an early header wide of the Eibar post, but the offside flag was raised and that was just about all that Barcelona created in the first 15 minutes against the confident visitors, who started well.
The home side did make the breakthrough in the 19th minute, however, when Luis Suarez combined with Philippe Coutinho before sweeping a low effort into the far corner of the net.
Coutinho has had his critics this season, but the Brazilian was named in the starting XI by Ernesto Valverde and repaid the faith by playing a key role in the Catalan giants making the breakthrough.
Sergi Roberto then saw a header miss the post down the other end during an open period of the match.
Eibar continued to have their moments as Fabian Orellana struck over the Barcelona crossbar in the 38th minute, before a series of crosses into the home side's box caused a lot of concern.
Barcelona thought that they should have had a penalty late in the first period when Coutinho went down under contact from Pena, but the officials were not interested and 1-0 was the score at the half-time break.
Eibar started the second half impressively, but Barcelona doubled their lead in the 53rd minute when Messi collected a clever pass from Luis Suarez before smashing the ball into the bottom corner of the net for his 400th La Liga goal.
Luis Suarez had a golden chance to score a second moments later when he met a cross inside the Eibar box, but Asier Riesgo was on hand to make a wonderful save.
The Uruguay international did have his second of the night in the 59th minute, however, when he stroked the ball past Riesgo with the outside of his foot following some lacklustre defending from the visitors.
Eibar are again enjoying another impressive campaign, but Barcelona were rampant in the period between their second and third goals, while the tempo remained high entering the final 30 minutes of action.
Ousmane Dembele had been replaced by Coutinho in the starting XI, but the France international was introduced in the 71st minute as Barcelona looked for more goals in the latter stages.
The champions had chances to add to the scoring in the latter stages, but 3-0 was how it finished on the night as Valverde's team continued their impressive run of La Liga form.
BARCELONA (4-3-3): Ter Stegen; Roberto (Semedo 83'), Pique, Lenglet, Alba; Rakitic, Busquets (Vidal 66'), Arthur (Dembele 71'); Coutinho, L Suarez, Messi
EIBAR (4-2-3-1): Riesgo; Pena, Bigas, Arbilla, Cote; Escalante (Kike 77'), Diop; Orellana, Jordan, Cucurella (De Blasis 65'); Enrich (Cardona 84')