  A chiral effective theory of quarks and diquarks is formulated and applied to
exotic tetraquarks and pentaquarks. The effective theory is similar to the
chiral quark effective theory with the addition of diquark degrees of freedom
and couplings to quarks. Chiral symmetry through generalized Goldberger-Treiman
relations, fixes the mass splitting between the even and odd parity diquarks to
be about 600 MeV. We provide an estimate of the parameters of the effective
theory from both the random instanton model and known data on the low lying
scalar nonet. We assess the static properties of the exotic baryons, such as
their masses, magnetic moments and decay widths. We show that the small decay
widths of the newly reported exotics are largely due to a large tunnelling
suppression of a quark between a pair of diquarks. We find $\Gamma(\Theta^+\to
K^+n)\simeq 2.5\sim7.0 MeV$ and $\Gamma(\Xi^{--}\to\Xi^- \pi^-)\simeq
1.7\sim4.8 MeV$.
