Timely and accurate diagnosis of plant pathogens is crucial for their better management preventing huge economic losses. Diagnosis based on symptoms, microscopic observation and cultural studies needs expertise on morphology and taxonomical aspects of the microorganisms. The advent of PCR and ELISA revolutionized the field of plant pathogen diagnosis, since then a number of techniques have been developed meeting wide requirements. Diagnostic techniques based on immunoassays, nucleic acid information, biochemical data are quite popular due to their accurate and rapid results however, this doesn’t limit the further developments in the respective aspects. Enose, Biolog and API are the new age bio-chemical based diagnostic techniques whereas, Isothermal amplification, Reverse Dot Blot Hybridization (RDBH), RNA-seq techniques are innovative based on nucleic acid information. High-through put sequencing has become a novel standard for detection of new organisms too. Integration of other technologies like spectral imaging, biosensors and nanotechnology have further widened the possibilities. In whole, this chapter is an attempt to summarize the advanced diagnostic techniques in the field of plant pathology.