Atherosclerosis and accompanying cardiovascular disease are the first causes of mortality in patients undergoing maintenance hemodialysis. Anti-atherosclerotic effects of hemodiafiltration (HDF) have been reported. Our study aimed to investigate the effect of serum derived from a healthy group (n = 23), before and after hemodialysis (HD) therapy (n = 23), and before and after HDF therapy (n = 17) on the expression of microRNA-33a and its target genes adenosine triphosphate-binding cassette transporter A1,G1 (ABCA1, ABCG1) in THP-1 macrophages. Meanwhile, blood lipids and high-sensitivity C-reactive protein (hs-CRP) were measured in these groups. Our data showed that the expression of miRNA-33a was lower (P < 0.05) and ABCA1 and ABCG1 were higher (P < 0.05) in the healthy group than pre-HD and pre-HDF. miR-33a was significantly decreased (P < 0.05) but ABCA1, ABCG1 was significantly increased (P < 0.05) in post-HDF compared with pre-HDF, while these parameters in pre- and post- HD groups did not show any significant change (P > 0.05). High density lipoprotein cholesterol (HDL-C) was higher and hs-CRP was lower in the healthy group than pre-HD and pre-HDF groups. Moreover, a significant increase of HDL-C (P < 0.05) and decrease (P < 0.05) of hs-CRP was shown in post-HDF compared with pre-HDF, but HD appeared to have no significant change in these subjects. HDF therapy can downregulate miR-33a expression, and then result in ABCA1, ABCG1 upregulation and an increase in circulating HDL-C, leading to a possible anti-atherosclerosis effect to some extent.