Cardioversion of atrial fibrillation (AF) >48 hours require exclusion of left atrial thrombus (LAT) through transesophageal echocardiography (TEE). However, availability of TEE is limited and left atrial appendage is not easily visualised by transthoracic echocardiography. The aim is to know whether d-dimer assay can be an alternative for TEE for detection of LAT in patients with AF >48 hours. We searched PubMed, EBSCOhost, Cochrane CENTRAL, EuropePMC, Proquest and used the snowballing technique. Two authors independently extracted and assessed the risk of bias. All observational studies and systematic reviews. After excluding duplicate, applying inclusion criteria and critical appraisal using Oxford CEBM tools, we include five studies. All five studies founded that D-dimer level significantly elevated in a group with LAA. In 4 out of 5 studies, the diagnostic performance as measured by AUC was > 0.70; with the sensitivity and specificity vary between 75.9% - 89% and 73.1% - 95%, respectively. However, there is no one reliable cut off point, as all of those studies used different cut-off point and a study even reported a sensitivity of only 35% at 500 ng/dl cut off value. D-dimer assay emerges as one of promising alternative diagnostic tool. However, we need more studies before integrating it into clinical practice.